Health A to Z

This is a comprehensive encyclopedia of over 500 conditions and diseases, with over 800 illustrations. Created by the faculty at Harvard Medical School, entries offer an overview of the condition along with a description of symptoms, diagnosis, tips for prevention, treatment options, prognosis, and advice about when to call a professional.

Abdominal Adhesions

Abdominal Aortic Aneurysm

Absence Seizures (Petit Mal Seizures)

Achalasia

ACL (Anterior Cruciate Ligament) Injuries

Acne

Acoustic Neuroma

Acute Bronchitis

Acute Lymphocytic Leukemia (ALL) in Adults

Acute Lymphocytic Leukemia (ALL) in Children

Acute Myeloid Leukemia (AML)

Acute Pancreatitis

Acute Prostatitis

Acute Sinusitis

Adenocarcinoma of the lung

Adrenocortical Carcinoma

Age Spots (Solar Lentigo, Liver Spots)

Aging Overview

Alcohol Use Disorder (Alcoholism)

Alcohol Withdrawal

Allergy Overview

Allergy Shots (Allergen Immunotherapy)

Amyotrophic Lateral Sclerosis (ALS)

Anal Cancer

Anal Disorders

Anal Itch (Pruritus Ani)

Ankylosing Spondylitis

Anorexia Nervosa

Antibiotic-Associated Diarrhea

Antiphospholipid Antibody Syndrome

Antisocial Personality Disorder

Aplastic Anemia

Appendicitis

Arm Fracture

Arthritis Associated With Inflammatory Bowel Disease

Asthma

Astigmatism

Asymptomatic Bacteriuria

Atherosclerosis

Athlete's Foot (Tinea Pedis)

Atrial Fibrillation

Attention-Deficit Hyperactivity Disorder (ADHD)

Autism (Autism Spectrum Disorder)

Back Pain

Bacterial Vaginosis (Gardnerella Vaginitis)

Balanitis

Barium Enema

Barotrauma

Bartholin's Gland Cyst

Basal Cell Carcinoma

Bedsores (Decubitus Ulcers)

Bedwetting (Enuresis)

Bipolar Disorder (Manic Depressive Illness or Manic Depression)

Black Eye

Bladder Cancer

Bladder Infection (Cystitis)

Blisters (Overview)

Body Lice

Boils and Carbuncles

Borderline Personality Disorder

Broken Nose (Nasal Fracture)

Carbon Monoxide Poisoning

Carcinoid Tumors of the Lung

Cardiac Arrhythmias

Cardiomyopathy

Carpal Tunnel Syndrome

Cataracts

Celiac Disease (Non-Tropical Sprue)

Chemical Injury to the Eye

Chickenpox (Varicella)

Chorionic Villus Sampling

Choroidal Melanoma

Chronic Fatigue Syndrome

Chronic Hepatitis

Chronic Laryngitis

Chronic Lymphocytic Leukemia (CLL)

Chronic Obstructive Pulmonary Disease (COPD)

Chronic Otitis Media, Cholesteatoma and Mastoiditis

Chronic Pancreatitis

Chronic Prostatitis

Chronic Sinusitis (in Adults)

Cirrhosis

Cluster Headache

Cogan's Syndrome

Collarbone (Clavicle) Fracture

Colon Polyps

Colorectal Cancer

Coma and Persistent Vegetative State

Common Cold (Viral Rhinitis)

Complex Regional Pain Syndrome (CRPS)

Concussion

Constipation and Impaction

Contact Dermatitis

Conversion Disorder (Functional Neurological Symptom Disorder)

Corneal Abrasion

Corns and Calluses

Coronary Artery Disease

Creutzfeldt-Jakob Disease (CJD)

Crohn's Disease

Crossed Eyes (Strabismus)

Croup

Curvature of the Penis (Peyronie's Disease)

Cystic Fibrosis

Cysts (Overview)

Cytomegalovirus (CMV)

Dandruff

Decompression Sickness

Developmental Dysplasia of the Hip

Deviated Septum

Diabetes Mellitus Overview

Diabetic Ketoacidosis

Diabetic Nephropathy

Diabetic Neuropathies

Diarrhea

Dislocated Lens

Diverticulosis and Diverticulitis

Double Vision (Diplopia)

Down Syndrome

Drooping Eyelid (Ptosis)

Dry Eye Syndrome

Dry Skin

Dysfunctional Uterine Bleeding

Encopresis (Fecal Soiling)

End-Stage Renal Disease

Endocarditis

Endometriosis

Endophthalmitis

Enlarged Prostate (Benign Prostatic Hyperplasia)

Epidemic Pleurodynia

Epidermoid Cyst

Epididymitis And Orchitis

Epiglottitis

Epilepsy

Esophageal Cancer

Esophageal Rings And Webs

Extragonadal Germ Cell Tumors

Eye Socket Fracture (Fracture Of The Orbit)

Fallen Arch

Fallopian Tube Cancer

Familial Dysautonomia

Farsightedness (Hyperopia)

Fifth Disease (Erythema Infectiosum)

Foreign Objects In The Ear

Fragile X Syndrome

Friction Blisters

Friedreich's Ataxia
Frostbite

Gallbladder and bile duct cancer

Gallstones

Gas (Flatulence)

Gastritis

Gastroenteritis In Adults

Gastroenteritis In Children

Gastroesophageal Reflux Disease (GERD)

Gastrointestinal Amebiasis

Gaucher Disease

Generalized Anxiety Disorder

Generalized Seizures (Grand Mal Seizures)

Genital Herpes

Genital Warts

Gestational Diabetes

Giant Cell Arteritis (Temporal Arteritis)

Giardiasis

Glaucoma

Glioblastoma Multiforme

Glomerulonephritis

Gonorrhea

Gout

Granulomatosis with polyangiitis

Graves' Disease

Graves' Eye Disease (Graves' Ophthalmopathy)

Guillain-Barre Syndrome

Hair Loss

Hammertoe

Hay Fever (Allergic Rhinitis)

Head and Neck Cancer

Head Injury In Adults

Head Injury In Children

Head Lice

Headache Overview

Hearing Loss in Adults

Hearing Loss in Children

Heart Attack (Myocardial Infarction)

Heart Failure

Heart Murmur

Heart Valve Problems

Heart Valve Replacement

Heat Stroke (Hyperthermia)

Hereditary-Patterned Baldness

High Blood Pressure (Hypertension)

High Cholesterol (Hypercholesterolemia)

Human Papilloma Virus (HPV)

Huntington's Disease (Chorea)

Illness Anxiety Disorder

Immune Thrombocytopenic Purpura (ITP)

Impetigo

Impotence (Erectile Dysfunction)

Infectious Arthritis

Infectious Mononucleosis

Ingrown Toenail

Inguinal Hernia

Insomnia

Interstitial Cystitis

Intracranial Aneurysms

Iron Deficiency

Irritable Bowel Syndrome (IBS)

Jet Lag

Jock Itch (Tinea Cruris)

Langerhans' Cell Histiocytosis (Histiocytosis X)

Lupus (Systemic Lupus Erythematosus)

Malignant Hyperthermia

Marfan Syndrome

Maturity Onset Diabetes of the Young (MODY)

Measles (Rubeola)

Meckel's Diverticulum

Menopause And Perimenopause

Mesothelioma

Metastatic Brain Tumors

Mid-Menstrual Cycle Pain (Mittelschmerz)

Middle-Ear Infection (Otitis Media)

Migraine

Miscarriage

Mitral Valve Prolapse

Molar Pregnancy

Moles (Nevi)

Molluscum Contagiosum

Myelodysplastic Syndromes

Nearsightedness (Myopia)

Non-Small Cell Lung Cancer

Nosebleed (Epistaxis)

Obesity

Obsessive-Compulsive Disorder (OCD)

Onycholysis

Optic Nerve Swelling (Papilledema)

Oral Cancer

Osgood-Schlatter Disease

Paget's Disease of Bone

Pain

Painful Sexual Intercourse (Dyspareunia)

Pancreatic Cancer

Pancreatitis Overview

Partial Seizures (Focal Seizures)

Pelvic Inflammatory Disease (PID)

Peptic Ulcer

Perforated Eardrum

Pericarditis

Peripheral Arterial Disease

Peritonsillar Abscess

Pertussis (Whooping Cough)

Phenylketonuria (PKU)

Phimosis and Paraphimosis

Phobia

Pinkeye (Conjunctivitis)

Pituitary Tumors

Pityriasis Rosea

Plague (Yersinia Pestis)

Plantar Fasciitis

Pleurisy And Pleural Effusion

Polycystic Kidney Disease

Polycystic Ovary Syndrome

Polymyalgia Rheumatica

Post-Polio Syndrome

Post-Traumatic Stress Disorder

Posterior Cruciate Ligament (PCL) Injuries

Postpartum Depression

Pre-Diabetes

Preeclampsia And Eclampsia

Premature Ejaculation

Premenstrual Syndrome (PMS)

Pubic Lice Or Crab Lice

Respiratory Syncytial Virus

Restless Legs Syndrome

Retinal Vessel Occlusion

Retrograde Ejaculation

Rocky Mountain Spotted Fever

Rosacea

Rotator Cuff Injury

Salivary Gland Disorders

Schizotypal Personality Disorder

Screening for Birth Defects in Early Pregnancy (Combined Test, Integrated Test, and Quadruple Test)

Sebaceous Cysts

Seborrheic Dermatitis

Seborrheic Keratoses

Secondary Hypertension

Sedative, Hypnotic or Anxiolytic Drug Use Disorder

Seizure Overview

Sexually Transmitted Diseases (Overview)

Shigellosis

Shin Splints

Shingles (Herpes Zoster)

Skin Tags (Acrochordon)

Sleep Apnea

Sleepwalking and Sleep Terrors

Smallpox

Soft Tissue Sarcoma

Somatic Symptom Disorder

Sore Throat (Pharyngitis)

Squamous Cell Carcinoma of the Lung

Squamous Cell Carcinoma of the Skin

Subarachnoid Hemorrhage

Subdural Hematoma

Sun Allergy (Photosensitivity)

Sun-Damaged Skin

Superficial Thrombophlebitis

Swallowed Object

Swimmer's Ear (Otitis Externa)

Tear Duct Infection (Dacryocystitis)

Telogen Effluvium

Tendonitis

Tennis Elbow (Lateral Epicondylitis)

Throat Cancer (Larynx and Pharynx)

Thrombocytopenia

Thromboembolism (Deep Vein Thrombosis and Pulmonary Embolism)

Toenail Fungus (Onychomycosis)

Transient Ischemic Attack (TIA)

Traumatic Dislocation of the Hip

Trichomoniasis

Trigeminal Neuralgia (Tic Douloureux)

Tropical Sprue

Tuberculosis

Type 1 Diabetes Mellitus

Type 2 Diabetes Mellitus

Urinary Tract Infection in Men

Urinary Tract Infection in Women

Uterine And Bladder Prolapse

Uterine Cancer

Uveitis

Vaginal Atrophy (Atrophic Vaginitis)

Vaginal Cancer

Vaginal Discharge

Vaginal Yeast Infection

Vitamin B12 Deficiency

Vitiligo

Vocal Cord Disorders

Vulvar Cancer

Waldenström Macroglobulinemia

Warts

Wax Blockage Of The Ear Canal

Wilms' Tumor

Wrist Sprain

Yaws

As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review or update on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

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