Fatigue: Clinical Meaning

Type 2 Diabetes

Type 2 diabetes is a chronic metabolic condition where the body becomes resistant to insulin or doesn't produce enough of it, causing blood sugar levels to rise. It is the most common form of diabetes, affecting hundreds of millions worldwide.

Bronchitis

Bronchitis is inflammation of the bronchial tubes that carry air to the lungs. Acute bronchitis is usually caused by viruses and resolves in 2–3 weeks. Chronic bronchitis is a form of COPD caused by long-term irritation, often from smoking.

Pneumonia

Pneumonia is an infection that inflames the air sacs (alveoli) in one or both lungs, which may fill with fluid or pus. It can be caused by bacteria, viruses, or fungi and ranges from mild to life-threatening.

Sinusitis

Sinusitis is inflammation of the sinuses, often following a cold or allergy. It causes facial pain, nasal congestion, thick nasal discharge, and reduced sense of smell. Acute sinusitis lasts up to 4 weeks; chronic sinusitis persists over 12 weeks.

Colitis (Ulcerative Colitis)

Ulcerative colitis is a chronic inflammatory bowel disease causing long-lasting inflammation and ulcers in the digestive tract, primarily affecting the colon and rectum. It leads to abdominal pain, diarrhea with blood, and urgency.

Hypothyroidism

Hypothyroidism occurs when the thyroid gland doesn't produce enough thyroid hormone. This slows metabolism and causes fatigue, weight gain, cold intolerance, constipation, and depression. Hashimoto's thyroiditis is the most common cause.

Hyperthyroidism

Hyperthyroidism occurs when the thyroid gland produces too much thyroid hormone, speeding up metabolism. It causes weight loss, rapid heartbeat, anxiety, tremors, and heat intolerance. Graves' disease is the most common cause.

Anemia

Anemia is a condition where the blood lacks enough healthy red blood cells or hemoglobin to carry adequate oxygen to tissues. Iron deficiency is the most common cause worldwide. Symptoms include fatigue, pallor, shortness of breath, and dizziness.

Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that causes inflammation in the joints, leading to pain, swelling, and eventual joint damage. Unlike osteoarthritis, RA is systemic and can affect organs including the heart and lungs.

Migraine

Migraine is a neurological disorder characterized by recurrent, severe headaches often accompanied by nausea, vomiting, and sensitivity to light and sound. Attacks can last 4–72 hours and significantly impair daily functioning.

Depression

Depression is a common and serious mood disorder causing persistent feelings of sadness, hopelessness, and loss of interest in activities. It affects how a person thinks, feels, and handles daily activities. Effective treatments include therapy and medication.

Anxiety Disorder

Anxiety disorders are among the most common mental health conditions, characterized by excessive fear, worry, or nervousness that interferes with daily activities. Types include generalized anxiety disorder (GAD), panic disorder, and social anxiety.

Epilepsy

Epilepsy is a neurological disorder characterized by recurrent, unprovoked seizures resulting from abnormal electrical activity in the brain. It affects people of all ages and can be managed with medication in most cases.

Parkinson's Disease

Parkinson's disease is a progressive neurological disorder affecting movement, caused by the loss of dopamine-producing neurons. Symptoms include tremor, rigidity, slowness of movement, and balance problems. There is no cure, but treatments can manage symptoms.

Alzheimer's Disease

Alzheimer's disease is the most common cause of dementia — a progressive neurological disorder that destroys memory and other cognitive functions. It typically begins with mild memory loss and progresses to severe cognitive impairment.

Heart Failure

Heart failure occurs when the heart cannot pump enough blood to meet the body's needs. It is a chronic condition that causes fatigue, shortness of breath, and fluid retention (edema). It requires ongoing medical management.

Cardiac Arrhythmia

Cardiac arrhythmia refers to irregular heart rhythms — the heart beats too fast, too slow, or with an irregular pattern. Some arrhythmias are harmless, while others (like atrial fibrillation) significantly increase the risk of stroke and heart failure.

Hepatitis

Hepatitis is inflammation of the liver, most commonly caused by viral infections (Hepatitis A, B, C, D, E). It can also result from alcohol use, toxins, or autoimmune conditions. Symptoms include jaundice, fatigue, abdominal pain, and dark urine.

Liver Cirrhosis

Liver cirrhosis is advanced scarring (fibrosis) of the liver caused by long-term damage from hepatitis, alcohol abuse, or fatty liver disease. As scar tissue replaces healthy tissue, the liver loses its ability to function properly.

Endometriosis

Endometriosis is a condition where tissue similar to the uterine lining grows outside the uterus. It causes chronic pelvic pain, especially during menstruation, and can lead to infertility. It affects approximately 10% of reproductive-age women.

PCOS (Polycystic Ovary Syndrome)

Polycystic ovary syndrome (PCOS) is a hormonal disorder common among women of reproductive age, causing irregular periods, excess androgen levels, and polycystic ovaries. It is associated with insulin resistance and increased risk of diabetes and heart disease.

Ankylosing Spondylitis

Ankylosing spondylitis is a type of inflammatory arthritis primarily affecting the spine and sacroiliac joints. It causes chronic pain and stiffness in the lower back and can lead to fusion of spinal vertebrae. It is more common in men.

Influenza (Flu)

Influenza is a highly contagious respiratory viral illness caused by influenza A or B viruses. It spreads through respiratory droplets and causes sudden fever, severe body aches, fatigue, cough, and headache. Annual vaccination is recommended for prevention.

Common Cold

The common cold is a viral upper respiratory infection, most often caused by rhinoviruses. Symptoms include runny nose, sneezing, sore throat, cough, and mild fever. It is usually self-limiting and resolves within 7–10 days.

COVID-19

COVID-19 is an infectious respiratory disease caused by the SARS-CoV-2 virus. Symptoms range from mild (fever, cough, fatigue) to severe (pneumonia, respiratory failure). Long COVID affects some patients with persistent symptoms lasting months.

Chickenpox (Varicella)

Chickenpox is a highly contagious viral infection caused by the varicella-zoster virus. It causes an itchy blister-like rash, fever, and fatigue. It primarily affects children but can be more severe in adults. Vaccination is available.

Measles

Measles is a highly contagious viral disease characterized by fever, cough, runny nose, red eyes, and a distinctive red blotchy rash. It can cause serious complications including pneumonia and encephalitis. MMR vaccination provides effective protection.

Whooping Cough (Pertussis)

Whooping cough is a highly contagious bacterial respiratory infection caused by Bordetella pertussis. It causes severe coughing fits followed by a high-pitched 'whoop' sound during breathing. It is most dangerous in infants. DTaP vaccination provides protection.

Lung Cancer

Lung cancer is the leading cause of cancer-related death worldwide, most commonly caused by smoking. It is categorized into non-small cell (NSCLC, 85%) and small cell (SCLC) types, with symptoms including persistent cough, blood in sputum, weight loss, and chest pain.

Breast Cancer

Breast cancer is the most common cancer in women worldwide, arising from the breast tissue. Early detection through mammography dramatically improves outcomes; treatment includes surgery, radiation, chemotherapy, and hormone therapy.

Colorectal Cancer

Colorectal cancer develops in the colon or rectum and is the third most common cancer globally. Risk factors include age over 50, family history, inflammatory bowel disease, and diet high in red/processed meat.

Ovarian Cancer

Ovarian cancer is the fifth leading cause of cancer death in women and often presents late due to vague symptoms. It originates in the ovaries and frequently spreads to the peritoneum before diagnosis.

Melanoma (Skin Cancer)

Melanoma is the most dangerous form of skin cancer, arising from melanocytes. UV radiation is the primary risk factor; early detection using the ABCDE criteria (Asymmetry, Border, Color, Diameter, Evolution) is critical for survival.

Bladder Cancer

Bladder cancer most commonly presents as painless blood in the urine (hematuria). Risk factors include smoking, occupational exposure to chemicals, and chronic bladder irritation; it has a high recurrence rate.

Kidney Cancer (Renal Cell Carcinoma)

Renal cell carcinoma is the most common kidney cancer in adults, often discovered incidentally on imaging. Symptoms include hematuria, flank pain, and a palpable mass; smoking and obesity are key risk factors.

Leukemia

Leukemia is a cancer of blood-forming tissues that disrupts normal blood cell production. It is classified by speed of progression (acute/chronic) and cell type (lymphocytic/myeloid), causing fatigue, bleeding, and infections.

Non-Hodgkin Lymphoma

Non-Hodgkin lymphoma is a group of blood cancers affecting the lymphatic system, presenting with painless swollen lymph nodes, fatigue, night sweats, and weight loss. It is more common than Hodgkin lymphoma.

Hodgkin Lymphoma

Hodgkin lymphoma is a type of lymphoma characterized by the presence of Reed-Sternberg cells. It typically affects young adults and is one of the most curable cancers with modern chemotherapy and radiation.

Multiple Myeloma

Multiple myeloma is a cancer of plasma cells in the bone marrow, causing bone pain, anemia, kidney damage, and recurrent infections. Symptoms arise from the accumulation of abnormal plasma cells.

Liver Cancer (Hepatocellular Carcinoma)

Hepatocellular carcinoma typically develops in the setting of chronic liver disease or cirrhosis due to hepatitis B, hepatitis C, or alcohol. It is a leading cause of cancer death globally.

Pancreatic Cancer

Pancreatic cancer has one of the lowest survival rates of all cancers, largely due to late-stage diagnosis. Symptoms include jaundice, weight loss, abdominal pain, and new-onset diabetes; most cases are adenocarcinomas.

Bone Cancer (Osteosarcoma)

Osteosarcoma is the most common primary bone cancer, predominantly affecting adolescents. It presents as bone pain and swelling, most often around the knee; treatment involves surgery and chemotherapy.

Endometrial Cancer

Endometrial cancer arises from the lining of the uterus and is the most common gynecological cancer in developed countries. Postmenopausal bleeding is the hallmark symptom; obesity and excess estrogen are major risk factors.

Mesothelioma

Mesothelioma is a rare cancer of the mesothelium lining the lungs, abdomen, or heart, almost exclusively caused by asbestos exposure. It has a long latency period (20-50 years) and a poor prognosis.

Bile Duct Cancer (Cholangiocarcinoma)

Cholangiocarcinoma arises from the bile duct epithelium and often presents with obstructive jaundice, weight loss, and abdominal pain. It is typically diagnosed at an advanced stage with limited treatment options.

Small Cell Lung Cancer

Small cell lung cancer is an aggressive neuroendocrine tumor strongly associated with heavy smoking. It grows rapidly, often presenting with mediastinal widening and paraneoplastic syndromes; it is sensitive to initial chemotherapy but frequently relapses.

Angina Pectoris

Angina pectoris is chest pain or discomfort caused by reduced blood flow to the heart muscle, usually due to coronary artery disease. Stable angina occurs predictably with exertion; unstable angina occurs at rest and is a medical emergency.

Aortic Stenosis

Aortic stenosis is narrowing of the aortic valve opening, restricting blood flow from the heart. It causes exertional chest pain, syncope, and heart failure; valve replacement is required for severe symptomatic disease.

Mitral Valve Disease

Mitral valve disease includes mitral regurgitation (valve leaking) and mitral stenosis (valve narrowing), causing symptoms of breathlessness, fatigue, and palpitations. Rheumatic heart disease is a major cause worldwide.

Infective Endocarditis

Infective endocarditis is an infection of the heart valve lining by bacteria (usually Streptococcus or Staphylococcus), causing fever, heart murmur, and embolic complications. IV drug use and dental procedures are key risk factors.

Myocarditis

Myocarditis is inflammation of the heart muscle, most commonly caused by viral infections (particularly enteroviruses). It can present with chest pain, shortness of breath, palpitations, and in severe cases, heart failure or sudden death.

Pericarditis

Pericarditis is inflammation of the pericardium (the sac surrounding the heart), causing sharp, pleuritic chest pain that improves when leaning forward. Viral infections are the most common cause; NSAIDs are the primary treatment.

Atherosclerosis

Atherosclerosis is the buildup of plaques (cholesterol, fat, calcium) inside artery walls, progressively narrowing the vessel lumen. It is the underlying cause of most heart attacks, strokes, and peripheral artery disease.

Hypotension (Low Blood Pressure)

Hypotension is defined as blood pressure below 90/60 mmHg, causing dizziness, fainting, and fatigue. Causes include dehydration, prolonged standing (orthostatic hypotension), heart problems, and certain medications.

Cardiomyopathy

Cardiomyopathy is disease of the heart muscle that impairs its ability to pump blood effectively. Types include dilated (most common), hypertrophic, and restrictive; causes range from genetic mutations to chronic alcohol use.

Multiple Sclerosis

Multiple sclerosis is a chronic autoimmune disease in which the immune system attacks the myelin sheath of nerve fibers in the central nervous system. It causes episodes of neurological symptoms including vision loss, muscle weakness, balance problems, and cognitive changes.

Amyotrophic Lateral Sclerosis (ALS)

ALS is a rapidly progressive neurodegenerative disease affecting motor neurons, causing progressive muscle weakness, paralysis, and respiratory failure. Most patients die within 3-5 years of diagnosis; riluzole and edaravone modestly slow progression.

Encephalitis

Encephalitis is inflammation of the brain parenchyma, most commonly caused by viral infections (herpes simplex, enteroviruses). It presents with fever, altered consciousness, seizures, and focal neurological deficits; early antiviral treatment is crucial.

Narcolepsy

Narcolepsy is a chronic sleep disorder causing overwhelming daytime sleepiness and sudden attacks of sleep, often accompanied by cataplexy (sudden muscle weakness). It results from loss of orexin-producing neurons in the hypothalamus.

Tension-Type Headache

Tension-type headache is the most common headache disorder, causing a dull, pressing, bilateral head pain described as a tight band. Stress, poor posture, and sleep deprivation are common triggers; it responds to simple analgesics.

Post-Concussion Syndrome

Post-concussion syndrome involves persistent symptoms (headache, dizziness, cognitive difficulties, mood changes) lasting weeks to months after a mild traumatic brain injury. Most patients recover fully with rest and gradual return to activity.

Myasthenia Gravis

Myasthenia gravis is an autoimmune neuromuscular disease causing fluctuating muscle weakness, typically worsening with activity. Antibodies against acetylcholine receptors at the neuromuscular junction impair signal transmission; treatment includes cholinesterase inhibitors and immunosuppressants.

Tuberculosis (TB)

Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis, primarily affecting the lungs with symptoms of chronic cough, night sweats, fever, and weight loss. Drug-resistant TB is a growing global health threat requiring prolonged combination antibiotic therapy.

Malaria

Malaria is a life-threatening parasitic disease transmitted by Anopheles mosquitoes, causing cyclical fever, chills, and anemia. Plasmodium falciparum causes the most severe form; artemisinin-based combination therapy is the first-line treatment.

Dengue Fever

Dengue fever is a mosquito-borne viral infection causing high fever, severe headache, muscle and joint pain, and a characteristic skin rash. Dengue hemorrhagic fever is a severe form with bleeding and organ impairment.

Typhoid Fever

Typhoid fever is caused by Salmonella typhi, transmitted through contaminated food and water, causing sustained fever, abdominal pain, and rose spots. Antibiotic treatment is effective; vaccination is recommended for travellers to endemic areas.

Hepatitis C

Hepatitis C is a blood-borne viral infection causing chronic liver inflammation that can progress to cirrhosis and liver cancer over decades. Direct-acting antiviral therapy achieves cure rates above 95%.

HIV/AIDS

HIV (Human Immunodeficiency Virus) destroys CD4 T-cells, progressively weakening the immune system until AIDS develops. Antiretroviral therapy suppresses viral load to undetectable levels, enabling near-normal life expectancy.

Lyme Disease

Lyme disease is a tick-borne bacterial infection caused by Borrelia burgdorferi, presenting with a bull's-eye rash (erythema migrans), flu-like symptoms, and if untreated, joint, neurological, and cardiac complications.

Shingles (Herpes Zoster)

Shingles is reactivation of the varicella-zoster virus (chickenpox virus) in sensory nerves, causing a painful, blistering rash in a dermatomal distribution. Post-herpetic neuralgia is a common and debilitating complication.

Infectious Mononucleosis (Mono)

Infectious mononucleosis, caused by Epstein-Barr virus, presents with severe fatigue, sore throat, swollen lymph nodes, and splenomegaly. It primarily affects adolescents and young adults; strenuous activity must be avoided due to spleen rupture risk.

Sepsis

Sepsis is a life-threatening systemic response to infection causing organ dysfunction. It is identified by abnormal temperature, heart rate, breathing, and altered mental status; prompt antibiotic treatment and fluid resuscitation are essential.

Toxoplasmosis

Toxoplasmosis is caused by the parasite Toxoplasma gondii, transmitted through cat feces, undercooked meat, or vertically to the fetus. It is usually asymptomatic in healthy individuals but can cause severe disease in immunocompromised patients and congenital infection.

Systemic Lupus Erythematosus (SLE)

SLE is a chronic autoimmune disease that can affect multiple organ systems including the skin, joints, kidneys, and nervous system. The characteristic butterfly rash, joint pain, and kidney disease are hallmarks; flares are managed with immunosuppressants.

Sjögren's Syndrome

Sjögren's syndrome is an autoimmune disease primarily affecting the salivary and lacrimal glands, causing dry eyes (xerophthalmia) and dry mouth (xerostomia). It can be primary or secondary to other autoimmune diseases like RA or lupus.

Crohn's Disease

Crohn's disease is a chronic inflammatory bowel disease that can affect any part of the GI tract from mouth to anus, causing abdominal pain, diarrhea, and malnutrition. Skip lesions and transmural inflammation are pathological hallmarks.

Celiac Disease

Celiac disease is an autoimmune reaction to gluten that damages the small intestine villi, impairing nutrient absorption. Symptoms include diarrhea, bloating, weight loss, and fatigue; strict gluten-free diet is the only treatment.

Sarcoidosis

Sarcoidosis is a multisystem inflammatory disease characterized by noncaseating granulomas, most commonly affecting the lungs and lymph nodes. It often resolves spontaneously but can cause progressive organ damage requiring corticosteroid treatment.

Vasculitis

Vasculitis is inflammation of blood vessel walls, causing a spectrum of diseases based on the size of affected vessels. Symptoms depend on the organs involved and can include skin purpura, peripheral neuropathy, and organ ischemia.

Polymyalgia Rheumatica

Polymyalgia rheumatica affects people over 50, causing severe aching and stiffness of the shoulders, hips, and neck that is worse in the morning. ESR and CRP are markedly elevated; it responds dramatically to corticosteroids.

Giant Cell Arteritis

Giant cell arteritis is a vasculitis of large arteries primarily affecting those over 50, causing headache, temporal artery tenderness, jaw claudication, and risk of sudden visual loss. Urgent corticosteroid treatment prevents blindness.

Antiphospholipid Syndrome

Antiphospholipid syndrome is an autoimmune disorder causing abnormal blood clotting, leading to deep vein thrombosis, pulmonary embolism, strokes, and recurrent miscarriages. Lifelong anticoagulation is the primary treatment.

Polymyositis

Polymyositis is an inflammatory myopathy causing progressive proximal muscle weakness, elevated muscle enzymes, and abnormal electromyography. Unlike dermatomyositis, it lacks the characteristic skin findings; treatment includes corticosteroids and immunosuppressants.

Dermatomyositis

Dermatomyositis is an inflammatory myopathy with characteristic skin manifestations including heliotrope rash around the eyes and Gottron's papules over the knuckles, combined with proximal muscle weakness. It is associated with increased cancer risk.

Behçet's Disease

Behçet's disease is a systemic vasculitis causing recurrent oral ulcers, genital ulcers, uveitis, and skin lesions. It is more prevalent along the ancient Silk Road and is managed with immunosuppressive therapy.

Goodpasture Syndrome

Goodpasture syndrome is an autoimmune disease in which antibodies target the glomerular and alveolar basement membranes, causing rapidly progressive glomerulonephritis and pulmonary hemorrhage. Plasmapheresis and immunosuppression are urgent treatments.

Scleroderma (Systemic Sclerosis)

Scleroderma is a chronic autoimmune disease causing skin hardening, fibrosis of internal organs (lungs, kidneys, GI tract), and vascular abnormalities. Raynaud's phenomenon is often an early manifestation; there is no cure.

Mixed Connective Tissue Disease

Mixed connective tissue disease (MCTD) has overlapping features of lupus, scleroderma, and polymyositis, associated with high titers of anti-U1-RNP antibodies. Pulmonary hypertension is a major complication.

Non-Alcoholic Fatty Liver Disease (NAFLD)

NAFLD is the accumulation of fat in liver cells not caused by alcohol, affecting up to 25% of adults globally. It ranges from simple steatosis to NASH (non-alcoholic steatohepatitis), which can progress to cirrhosis; lifestyle modification is the primary treatment.

Type 1 Diabetes

Type 1 diabetes is an autoimmune disease in which the immune system destroys insulin-producing beta cells in the pancreas, requiring lifelong insulin therapy. It typically develops in childhood or adolescence and accounts for 5-10% of all diabetes cases.

Prediabetes

Prediabetes is a metabolic state where blood glucose levels are elevated above normal but not high enough for a diabetes diagnosis. It affects over 400 million people globally and can progress to type 2 diabetes without lifestyle intervention.

Cushing's Syndrome

Cushing's syndrome results from prolonged exposure to high cortisol levels, causing central obesity, moon face, buffalo hump, skin thinning, and hypertension. The most common cause is exogenous corticosteroid use; endogenous causes include pituitary or adrenal tumors.

Addison's Disease

Addison's disease is primary adrenal insufficiency causing insufficient production of cortisol and aldosterone. Symptoms include fatigue, weight loss, hyperpigmentation, low blood pressure, and salt craving; lifelong hormone replacement is required.

Hyperparathyroidism

Primary hyperparathyroidism is caused by overactive parathyroid glands producing excess PTH, leading to hypercalcemia, bone loss, kidney stones, and GI symptoms. Most cases are caused by a benign parathyroid adenoma.

Hypoparathyroidism

Hypoparathyroidism results from insufficient PTH production, causing low calcium levels (hypocalcemia) with muscle cramps, tetany, numbness, and seizures. It most commonly occurs after thyroid or parathyroid surgery.

Pituitary Adenoma

Pituitary adenomas are benign tumors of the pituitary gland that can cause hormonal excess (functioning) or compressive symptoms (headache, visual field defects). Prolactinomas are the most common type; treatment includes medication, surgery, or radiation.

Testosterone Deficiency (Low T)

Testosterone deficiency (hypogonadism) in men causes fatigue, decreased libido, erectile dysfunction, mood changes, and loss of muscle mass. Causes include aging, pituitary disorders, and testicular disease; hormone replacement therapy is the primary treatment.

Metabolic Syndrome

Metabolic syndrome is a cluster of conditions (abdominal obesity, hypertension, hyperglycemia, low HDL cholesterol, high triglycerides) that together significantly increase cardiovascular and diabetes risk. Lifestyle modification is the cornerstone of management.

Obesity

Obesity is defined as a BMI above 30 and is associated with increased risk of type 2 diabetes, heart disease, stroke, sleep apnea, and certain cancers. It results from a complex interaction of genetic, behavioral, and environmental factors.

Vitamin D Deficiency

Vitamin D deficiency impairs calcium absorption and bone mineralization, causing bone pain, muscle weakness, fatigue, and increased fracture risk. It is extremely common globally due to limited sun exposure and dietary insufficiency.

Iron Deficiency Anemia

Iron deficiency anemia is the most common nutritional deficiency worldwide, caused by inadequate dietary intake, blood loss, or malabsorption. It causes fatigue, pallor, shortness of breath, and pica; iron supplementation is the treatment.

Pernicious Anemia

Pernicious anemia is an autoimmune condition in which antibodies against intrinsic factor prevent vitamin B12 absorption, causing megaloblastic anemia and neurological complications. Intramuscular B12 injections bypass the absorption defect.

Polycythemia Vera

Polycythemia vera is a myeloproliferative neoplasm causing overproduction of red blood cells, increasing blood viscosity and thrombosis risk. Symptoms include headache, itching after bathing, facial redness, and splenomegaly; phlebotomy is a primary treatment.

Hemochromatosis (Iron Overload)

Hereditary hemochromatosis is a genetic disorder causing excessive iron absorption and accumulation in organs (liver, heart, pancreas, joints), leading to cirrhosis, cardiomyopathy, and diabetes. Therapeutic phlebotomy is the standard treatment.

COPD (Chronic Obstructive Pulmonary Disease)

COPD is a progressive lung disease causing persistent airflow limitation, primarily from emphysema and chronic bronchitis. Smoking is responsible for 85% of cases; symptoms include chronic cough, sputum production, and exertional dyspnea.

Pulmonary Fibrosis

Pulmonary fibrosis is progressive scarring of lung tissue, causing worsening breathlessness, dry cough, and reduced exercise tolerance. Idiopathic pulmonary fibrosis (IPF) has a median survival of 3-5 years; antifibrotic drugs slow progression.

Pulmonary Hypertension

Pulmonary hypertension is elevated pressure in the pulmonary arteries, causing progressive exertional dyspnea, syncope, and right heart failure. It is classified into five groups based on etiology; targeted therapies improve outcomes in pulmonary arterial hypertension.

Obstructive Sleep Apnea

Obstructive sleep apnea involves repeated upper airway collapse during sleep, causing snoring, apneas, and daytime sleepiness. It affects over 1 billion people and is associated with hypertension, atrial fibrillation, and cognitive impairment; CPAP is the gold standard treatment.

Bronchiectasis

Bronchiectasis is permanent dilation and scarring of the bronchi, causing chronic productive cough, recurrent infections, and progressive lung damage. Common causes include recurrent pneumonia, cystic fibrosis, and primary ciliary dyskinesia.

Lung Abscess

A lung abscess is a pus-filled cavity in the lung parenchyma, usually caused by aspiration of oral bacteria in patients with impaired consciousness. It presents with productive cough, fever, and weight loss; prolonged antibiotics are the primary treatment.

Alpha-1 Antitrypsin Deficiency

Alpha-1 antitrypsin deficiency is a genetic disorder causing insufficient production of a protease inhibitor, leading to early-onset emphysema (especially in smokers) and liver disease. Augmentation therapy is available for the lung manifestations.

Hypersensitivity Pneumonitis

Hypersensitivity pneumonitis (extrinsic allergic alveolitis) is an inflammatory lung disease caused by repeated inhalation of organic antigens. Farmer's lung and bird fancier's lung are classic examples; antigen avoidance is the most important intervention.

Chronic Kidney Disease (CKD)

CKD is progressive, irreversible loss of kidney function over months to years, classified in stages 1-5 based on GFR. Diabetes and hypertension are the leading causes; management focuses on slowing progression and managing complications.

Acute Kidney Injury (AKI)

AKI is a sudden decrease in kidney function over hours to days, causing accumulation of waste products and fluid and electrolyte imbalances. Pre-renal (dehydration), intrinsic renal, and post-renal (obstruction) causes must be distinguished.

Glomerulonephritis

Glomerulonephritis is inflammation of the glomeruli causing hematuria, proteinuria, hypertension, and impaired kidney function. It can be acute (post-streptococcal) or chronic; IgA nephropathy is the most common form worldwide.

Nephrotic Syndrome

Nephrotic syndrome is characterized by massive proteinuria (>3.5g/day), hypoalbuminemia, edema, and hyperlipidemia. Causes include minimal change disease (children), membranous nephropathy, and diabetic nephropathy; steroids and immunosuppressants are used.

Renal Artery Stenosis

Renal artery stenosis is narrowing of the arteries supplying the kidneys, causing renovascular hypertension that is resistant to standard treatment and can lead to ischemic nephropathy. Atherosclerosis and fibromuscular dysplasia are the main causes.

Bipolar Disorder

Bipolar disorder involves episodes of mania (elevated mood, decreased need for sleep, impulsivity) alternating with depression. It affects approximately 2.4% of the global population; mood stabilizers (lithium, valproate) are the primary pharmacological treatment.

Anorexia Nervosa

Anorexia nervosa is an eating disorder with severe food restriction, intense fear of weight gain, and distorted body image. It has the highest mortality rate of any psychiatric disorder; multidisciplinary treatment including nutritional rehabilitation and psychotherapy is essential.

Bulimia Nervosa

Bulimia nervosa involves recurrent episodes of binge eating followed by compensatory behaviors (purging, laxative use, excessive exercise). Dental erosion, electrolyte abnormalities, and esophageal damage are common complications; CBT is first-line treatment.

Substance Use Disorder

Substance use disorder involves compulsive use of substances despite harmful consequences, including alcohol, opioids, stimulants, and cannabis. It is a chronic brain disorder; treatment includes behavioral therapies, medications (methadone, naltrexone, buprenorphine), and support groups.

Fibromyalgia

Fibromyalgia is a chronic condition causing widespread musculoskeletal pain, fatigue, sleep disturbance, and cognitive difficulties ("fibro fog"). Central sensitization is the underlying mechanism; multimodal treatment includes exercise, cognitive behavioral therapy, and medications.

Chronic Sinusitis

Chronic sinusitis is sinus inflammation lasting more than 12 weeks, causing nasal congestion, facial pressure, postnasal drip, and reduced sense of smell. It is subdivided into forms with and without nasal polyps; treatment includes nasal steroids, saline irrigation, and sometimes surgery.

Tonsillitis

Tonsillitis is inflammation of the palatine tonsils, causing sore throat, difficulty swallowing, fever, and swollen glands. Recurrent bacterial tonsillitis may require tonsillectomy; Group A Streptococcus is the most important bacterial cause.

Premature Ovarian Insufficiency

Premature ovarian insufficiency (POI) is loss of normal ovarian function before age 40, causing infertility, irregular or absent periods, hot flashes, and accelerated bone loss. Hormone replacement therapy is recommended until the natural age of menopause.

Gestational Diabetes

Gestational diabetes is hyperglycemia first detected during pregnancy, increasing risks of macrosomia, birth complications, and future type 2 diabetes in both mother and child. Management includes dietary modification, exercise, and insulin if needed.

Mastitis

Mastitis is inflammation of the breast tissue, most commonly occurring during breastfeeding due to blocked milk ducts or bacterial infection (S. aureus). It causes breast pain, redness, warmth, and fever; antibiotics and continued breastfeeding are recommended.

Chronic Fatigue Syndrome (ME/CFS)

Myalgic encephalomyelitis/chronic fatigue syndrome is a complex, debilitating condition causing profound fatigue not improved by rest, post-exertional malaise, cognitive difficulties, and sleep disturbances lasting over 6 months. No curative treatment exists; management focuses on symptom relief and pacing.

Interstitial Lung Disease

ILD encompasses a diverse group of lung disorders causing progressive scarring of lung tissue between the air sacs, reducing oxygen exchange. Symptoms include progressive breathlessness and dry cough; corticosteroids and antifibrotic drugs are used.

Long COVID (Post-COVID Syndrome)

Long COVID refers to persistent symptoms lasting more than 12 weeks after acute COVID-19 infection, including fatigue, brain fog, breathlessness, and chest pain. Post-exertional malaise and autonomic dysfunction are prominent features; management is multimodal and symptom-based.

Giardiasis

Giardiasis is a common intestinal infection caused by the protozoan parasite Giardia lamblia, transmitted through contaminated water or food. It presents with chronic diarrhoea, bloating, and malabsorption, and is treated with metronidazole or tinidazole.

Enterobiasis (Pinworm Infection)

Enterobiasis is the most common helminthic infection in temperate countries, caused by Enterobius vermicularis. It predominantly affects children and presents with intense nocturnal perianal itching. Treatment is with mebendazole or albendazole.

Ascariasis

Ascariasis is the most prevalent human helminthic infection worldwide, caused by Ascaris lumbricoides. It can cause pulmonary symptoms during larval migration and intestinal obstruction in heavy infections. Albendazole is the drug of choice.

Trichinellosis

Trichinellosis is caused by Trichinella spiralis larvae encysted in muscle tissue, typically acquired from eating undercooked pork or wild game. It presents with fever, periorbital oedema, and severe myalgia. Treatment includes mebendazole and corticosteroids.

Echinococcosis (Hydatid Disease)

Echinococcosis is caused by larval stages of Echinococcus tapeworms, forming slowly growing cysts primarily in the liver and lungs. It is acquired from contact with infected dogs or contaminated food. Surgical removal and albendazole are the main treatments.

Leishmaniasis

Leishmaniasis is caused by Leishmania protozoa transmitted by sandfly bites, presenting in visceral, cutaneous, or mucocutaneous forms. Visceral leishmaniasis (kala-azar) causes fever, splenomegaly, and pancytopaenia. Amphotericin B and miltefosine are first-line treatments.

Taeniasis (Tapeworm Infection)

Taeniasis is intestinal infection by Taenia solium or Taenia saginata tapeworms, acquired by eating undercooked pork or beef. Symptoms include abdominal discomfort and weight loss. Neurocysticercosis (T. solium larvae in the CNS) is the most severe complication. Praziquantel is curative.

Strongyloidiasis

Strongyloidiasis is caused by Strongyloides stercoralis, a soil-transmitted nematode capable of autoinfection and chronic persistence for decades. In immunocompromised patients, hyperinfection syndrome can be life-threatening. Ivermectin is the treatment of choice.

Viral Pharyngitis

Viral pharyngitis is throat inflammation caused by a viral infection, most commonly rhinovirus or adenovirus. It is the most frequent cause of sore throat and resolves without antibiotics.

Acute Laryngitis

Acute laryngitis is sudden inflammation of the larynx typically caused by viral upper respiratory infections. The hallmark is hoarseness or voice loss, usually lasting less than 3 weeks.

Pleurisy

Pleurisy is inflammation of the pleural membranes surrounding the lungs, causing sharp chest pain that worsens when breathing deeply or coughing.

Pulmonary Edema

Pulmonary edema is excess fluid accumulation in the lungs making breathing difficult. Most cases result from heart problems, though non-cardiac causes also exist.

Atrial Fibrillation

Atrial fibrillation (AFib) is the most common cardiac arrhythmia, characterized by rapid and irregular atrial beating. It significantly increases stroke and heart failure risk.

Burnout Syndrome

Burnout is a state of chronic stress leading to physical and emotional exhaustion, cynicism, and feelings of ineffectiveness. The WHO recognizes it as an occupational phenomenon.

Menopause

Menopause marks the end of menstrual cycles after 12 consecutive months without a period, typically in women's late 40s to early 50s. Significant hormonal changes cause wide-ranging symptoms.

Vitamin B12 Deficiency

Vitamin B12 deficiency is essential for nerve function, red blood cell formation, and DNA synthesis. Particularly common in older adults, vegetarians, and those with GI disorders.

Magnesium Deficiency

Magnesium deficiency affects an estimated 10-30% of the population. Magnesium is involved in over 300 enzymatic reactions in the body, making deficiency wide-ranging in effects.

Psoriatic Arthritis

Psoriatic arthritis is inflammatory arthritis affecting some people with psoriasis. It causes joint pain, stiffness and swelling ranging from mild to severe with potential for joint damage.

Reactive Arthritis

Reactive arthritis is joint inflammation triggered by an infection elsewhere in the body, usually intestines, genitals, or urinary tract. The classic triad includes joint, eye, and urethral inflammation.

Premenstrual Syndrome (PMS)

PMS encompasses physical and emotional symptoms occurring before menstruation, resolving with the onset of the period. It affects up to 75% of menstruating women to some degree.

Sleep Deprivation

Sleep deprivation occurs when an individual gets insufficient sleep. Chronic sleep loss affects nearly every physiological system and increases risks of obesity, diabetes, cardiovascular disease, and mental health disorders.

Vitamin C Deficiency (Scurvy)

Vitamin C deficiency in its severe form causes scurvy. Subclinical deficiency affecting immune function and wound healing is more common in developed countries.

Zinc Deficiency

Zinc deficiency affects approximately 2 billion people worldwide, impacting immunity, wound healing, protein synthesis, and taste and smell.

Iodine Deficiency

Iodine deficiency is the leading preventable cause of intellectual disability worldwide. The thyroid requires iodine to produce hormones; deficiency leads to hypothyroidism and goiter.

Dehydration

Dehydration occurs when the body loses more fluid than it takes in. Even mild dehydration (1-2% body weight) can impair cognitive and physical performance.

Heat Exhaustion

Heat exhaustion is a heat-related illness after prolonged exposure to high temperatures with dehydration. It is a precursor to heat stroke and requires prompt cooling and rehydration.

Hypoglycemia

Hypoglycemia is low blood sugar, typically below 70 mg/dL. Most common in people with diabetes, it causes rapid neurological and adrenaline-driven symptoms requiring prompt treatment.

Hypercalcemia

Hypercalcemia is elevated blood calcium, most commonly caused by overactive parathyroid glands or cancer. Symptoms follow the mnemonic 'bones, stones, groans, and psychic moans'.

Adrenal Insufficiency

Adrenal insufficiency occurs when adrenal glands fail to produce sufficient cortisol. Primary (Addison's disease) is from adrenal damage; secondary is from pituitary or hypothalamic dysfunction.

Kidney Infection (Pyelonephritis)

Pyelonephritis is bacterial infection of one or both kidneys, usually ascending from a bladder infection. It requires prompt antibiotics to prevent kidney damage and sepsis.

Labyrinthitis

Labyrinthitis is inflammation of the inner ear labyrinth, typically following a viral infection. It causes sudden severe vertigo, hearing loss, and tinnitus, significantly impacting daily functioning.

Tinnitus

Tinnitus is the perception of noise or ringing in the ears without an external source. It affects 15-20% of people and can significantly impact sleep, concentration, and quality of life.

Giant Cell Arteritis

Giant cell arteritis is inflammation of large and medium arteries in the head. Primarily affecting people over 50, it can cause vision loss if untreated with corticosteroids.

Granulomatosis with Polyangiitis

Granulomatosis with polyangiitis (Wegener's) is a rare form of vasculitis affecting small and medium vessels, primarily targeting the respiratory tract and kidneys.

Primary Biliary Cholangitis

Primary biliary cholangitis is a chronic autoimmune liver disease causing progressive bile duct destruction. Left untreated it leads to liver cirrhosis.

Premenstrual Dysphoric Disorder (PMDD)

PMDD is a severe form of PMS causing marked emotional and physical symptoms in the week before menstruation. It significantly impairs daily functioning and responds to hormonal and psychiatric treatments.

Anemia

Anemia is a condition where there are insufficient healthy red blood cells to carry adequate oxygen to body tissues. It has many causes including nutritional deficiencies, chronic disease, and blood loss.

Viral Meningitis

Viral meningitis is inflammation of the membranes surrounding the brain and spinal cord caused by viruses. Less severe than bacterial meningitis, most cases resolve without specific treatment.

Hepatitis A

Hepatitis A is a highly contagious liver infection caused by the hepatitis A virus, transmitted through contaminated food and water. Unlike hepatitis B and C, it does not cause chronic disease.

Hay Fever (Allergic Rhinitis)

Hay fever (allergic rhinitis) is an allergic reaction to airborne allergens like pollen, dust mites, or pet dander. It is one of the most common allergic conditions, affecting up to 30% of the population.

Chronic Vertigo

Chronic vertigo encompasses multiple conditions causing persistent or recurrent episodes of dizziness and spinning sensation. Common causes include BPPV, Meniere's disease, vestibular migraine, and labyrinthitis.

Post-Concussion Syndrome

Post-concussion syndrome occurs when concussion symptoms last beyond the expected recovery period. Symptoms can persist for months or even years and require multidisciplinary management.

Mast Cell Activation Syndrome

Mast cell activation syndrome causes recurring episodes of anaphylaxis-like symptoms due to inappropriate mast cell activation. Diagnosis requires demonstration of abnormal mediator release.

Autoimmune Hepatitis

Autoimmune hepatitis is chronic liver inflammation where the immune system attacks liver cells. It can lead to cirrhosis if untreated but generally responds well to immunosuppressive therapy.

Non-Alcoholic Fatty Liver Disease

NAFLD is excessive fat buildup in the liver of people who drink little or no alcohol. It ranges from simple steatosis to non-alcoholic steatohepatitis (NASH) with inflammation and fibrosis.

Obstructive Sleep Apnea

OSA is a common sleep disorder where the throat muscles intermittently relax and block the airway during sleep. Untreated, it significantly increases cardiovascular disease risk.

Pulmonary Arterial Hypertension

Pulmonary arterial hypertension is high blood pressure in the arteries supplying the lungs. It causes the right side of the heart to work harder, eventually leading to heart failure.

Cardiac Tamponade

Cardiac tamponade is a life-threatening emergency where fluid accumulates in the pericardial sac, compressing the heart and impairing its ability to pump blood effectively.

Infective Endocarditis

Infective endocarditis is infection of the inner heart lining, particularly the heart valves. It is a serious condition requiring prolonged intravenous antibiotics and sometimes surgery.

Myocarditis

Myocarditis is inflammation of the heart muscle, most commonly caused by viral infections. It can affect the heart's electrical system and pumping ability, ranging from mild to life-threatening.

Diabetic Ketoacidosis

Diabetic ketoacidosis (DKA) is a life-threatening complication of diabetes in which the body produces dangerously high levels of blood acids called ketones. It most commonly affects people with type 1 diabetes and requires emergency treatment.