Diseases & Symptoms

Fibrosis is the excessive buildup of extracellular matrix that scars and stiffens tissue, and can lead to organ failure if it persists.

Food allergy is an adverse immune response to food proteins. Its most serious form, IgE-mediated, can cause life-threatening anaphylaxis, and treatment is still mainly avoidance.

Gallstones are hardened deposits that form from bile components in the gallbladder or bile ducts, causing pain and complications in some people.

Gastroenteritis is inflammation of the gastrointestinal tract, usually caused by infection, that produces diarrhea, vomiting, and abdominal discomfort.

A chronic condition in which stomach contents flow back into the esophagus, causing troublesome symptoms or mucosal injury. Covers its mechanisms, diagnosis, and treatment.

Germ theory explains infectious diseases as consequences of specific biological agents interacting with susceptible hosts and their environments.

Gestational diabetes is pregnancy-associated hyperglycemia that affects maternal and infant health and signals an increased risk of later diabetes.

A group of progressive optic neuropathies that damage the optic nerve and can cause irreversible vision loss, often linked to raised intraocular pressure.

Gout is a chronic arthritis caused by urate crystals deposited in joints, typically producing acute, painful attacks in one joint, often in the lower limb, and risking joint damage if untreated.

Graves’ disease is an autoimmune disorder that usually causes hyperthyroidism and may also affect the eyes and skin.

Hair loss (alopecia) is the thinning or absence of hair caused by disruption of the growth cycle, follicle damage, or genetic, immune, hormonal, and other factors.

Headache is pain in the head that may arise from a primary headache disorder or occur as a symptom of another condition.

Hearing loss is a partial or complete reduction in the ability to detect sound. It can be conductive, sensorineural, or mixed, and it is a leading global cause of disability.

Red blood cell destruction in the body or outside it, with clinical, laboratory, and microbiological significance.

A rare inherited bleeding disorder caused by deficiency of clotting factor VIII (hemophilia A) or factor IX (hemophilia B), mostly affecting males.

A viral infection of the liver caused by hepatitis B virus, which can cause acute or chronic disease; chronic infection carries major risks of cirrhosis and liver cancer.

A bloodborne viral infection of the liver caused by hepatitis C virus, which can become chronic but is curable with antiviral drugs.

A herniated disc is a spinal disc whose soft inner core protrudes through a tear in its outer ring, often compressing nearby nerves and causing pain, numbness or weakness.

Herpes simplex is a lifelong viral infection caused by HSV-1 and HSV-2, which establish latency in nerve cells and cause recurrent blisters or ulcers.

Human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS): virology, pathogenesis, treatment, prevention, and global public health.

HPV infection is a common sexually transmitted viral infection of skin and mucosa that usually clears on its own, but persistent high-risk types cause nearly all cervical cancers and contribute to other cancers.

Hyperglycemia is an abnormally high blood glucose concentration, commonly associated with diabetes but also occurring during illness, physiological stress, or medication use.

Abnormally high blood lipid levels that raise the risk of atherosclerotic cardiovascular disease.

Hypertension (high blood pressure) is a chronic condition in which arterial blood pressure stays persistently elevated. It is a leading modifiable risk factor for cardiovascular disease and premature death.

Hyperthyroidism is a set of disorders in which the thyroid gland makes excess thyroid hormone, causing a hypermetabolic state. Graves disease is its most common cause.

Hypoglycemia is abnormally low blood glucose that can impair brain function, most often arising from diabetes treatment or from disorders of glucose regulation.

Hypothyroidism is insufficient thyroid hormone activity, affecting metabolism, organ function, growth, and development.

Immunodeficiency is impaired immune function that increases susceptibility to infections and may accompany disturbances of immune regulation.

A disease caused by an infectious agent, whose development depends on the agent, the host’s defenses, and environmental conditions.

Inflammatory bowel disease (IBD) is a group of chronic, relapsing immune-mediated inflammatory disorders of the gastrointestinal tract, mainly Crohn's disease and ulcerative colitis.

A contagious respiratory illness caused by influenza viruses, producing seasonal epidemics, occasional pandemics and zoonotic spillover.

Insomnia is a common sleep disorder marked by persistent difficulty falling or staying asleep, with daytime impairment.

Insulin resistance is reduced tissue responsiveness to insulin, affecting glucose and lipid metabolism and contributing to type 2 diabetes.

Intracerebral hemorrhage is bleeding within brain tissue, causing neurological injury and, when spontaneous, a form of hemorrhagic stroke.

Anemia caused by insufficient iron for hemoglobin production, with nutritional, bleeding-related, and malabsorptive causes.

Pain felt in one or more joints (arthralgia). It is a symptom with many possible causes, from injury and degenerative wear to inflammatory, infectious, and systemic diseases.

Hard mineral deposits that form in the kidney and urinary tract, causing pain, obstruction, infection and recurrence.

Klinefelter syndrome is a sex chromosome condition, usually involving a 47,XXY karyotype, with variable effects on development, testicular function, and fertility.

Leukemia is a group of cancers of blood-forming cells, classified by cellular lineage, disease progression, and genetic characteristics.

Liver cancer is a malignant tumor of the liver, mainly hepatocellular carcinoma, usually arising from long-standing injury such as chronic hepatitis, cirrhosis, or fatty liver disease, and it is a leading cause of cancer death worldwide.

Low back pain is pain in the lumbar region, encompassing nonspecific symptoms and pain associated with identifiable spinal or other disorders.

A group of malignant lung tumors with distinct biological types, risk factors, diagnostic methods, and treatments.

Lymphedema is chronic tissue swelling caused by impaired lymphatic drainage, arising from developmental abnormalities or acquired lymphatic damage.

Lymphoma is a diverse group of cancers arising from lymphocytes, with subtypes that differ in biology, clinical course, and treatment.

A mosquito-borne parasitic disease caused by Plasmodium, covering its biology, clinical course, treatment, prevention, history, and global burden.

A highly contagious viral disease caused by measles virus, covering its biology, clinical course, vaccination, global elimination efforts, and current resurgence.

A mental disorder is a clinically significant disturbance in cognition, emotion, or behavior, classified by systems such as DSM-5-TR and ICD-11.

Harm caused by mercury in its elemental, inorganic, or organic (especially methylmercury) forms, with the nervous system and developing fetus most affected.

Migraine is a recurrent, disabling neurological disorder marked by attacks of head pain, often one-sided and throbbing, with nausea and sensory sensitivity.

Multiple myeloma is a cancer of plasma cells that can damage bones, impair kidney function, disrupt blood-cell production, and weaken immunity.

Multiple sclerosis is a chronic immune-mediated disease that damages myelin and nerve fibers in the central nervous system.

A group of clonal bone marrow cancers characterized by ineffective blood-cell production, cytopenias, and a variable risk of acute myeloid leukemia.

Myopia is a refractive condition that blurs distance vision and, particularly at higher degrees, increases the risk of sight-threatening eye disease.

An unpleasant sensation, usually felt in the upper abdomen, often with an urge to vomit. It reflects brain–gut signalling and has many possible causes.

A noncommunicable disease is a condition not ordinarily transmitted between people, often requiring long-term prevention, treatment, or care.

Obesity is a chronic, multifactorial condition of excess body fat that raises the risk of many serious diseases and is a major global public health problem.

A chronic mental disorder marked by intrusive, unwanted thoughts and repetitive behaviours or mental acts performed to relieve the anxiety they cause.

Osteoarthritis is a chronic whole-joint disease involving tissue damage, pain, stiffness, and variable loss of function.

A systemic skeletal disease in which reduced bone mass and deteriorated bone microarchitecture make bones fragile and prone to fracture.

Inflammation of the middle ear, most common in young children; covers acute infection, fluid without infection, and chronic drainage with perforation.