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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)

ACL (Anterior Cruciate Ligament) Injuries

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)

Alcohol Use Disorder (Alcoholism)

Alcohol Withdrawal

Allergy Overview

Allergy Shots (Allergen Immunotherapy)

Alopecia Areata

Altitude Sickness

Alzheimer's Disease

Amyotrophic Lateral Sclerosis (ALS)

Anal Itch (Pruritus Ani)

Anemia Overview

Ankylosing Spondylitis

Anorexia Nervosa

Antibiotic-Associated Diarrhea

Antiphospholipid Antibody Syndrome

Antisocial Personality Disorder

Aplastic Anemia

Arthritis Associated With Inflammatory Bowel Disease

Asymptomatic Bacteriuria

Atherosclerosis

Athlete's Foot (Tinea Pedis)

Atrial Fibrillation

Attention-Deficit Hyperactivity Disorder (ADHD)

Autism (Autism Spectrum Disorder)

Bacterial Vaginosis (Gardnerella Vaginitis)

Bartholin's Gland Cyst

Basal Cell Carcinoma

Bedsores (Decubitus Ulcers)

Bedwetting (Enuresis)

Behcet's Disease

Bile Duct Diseases

Bipolar Disorder (Manic Depressive Illness or Manic Depression)

Bladder Infection (Cystitis)

Blisters (Overview)

Boils and Carbuncles

Borderline Personality Disorder

Bowel Obstruction

Brain Tumor Overview

Broken Nose (Nasal Fracture)

Campylobacteriosis

Cancer Overview

Carbon Monoxide Poisoning

Carcinoid Tumors of the Lung

Cardiac Arrhythmias

Carpal Tunnel Syndrome

Celiac Disease (Non-Tropical Sprue)

Cervical Cancer

Cervical Polyps

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)

Cluster Headache

Cogan's Syndrome

Collarbone (Clavicle) Fracture

Colorectal Cancer

Coma and Persistent Vegetative State

Common Cold (Viral Rhinitis)

Complex Regional Pain Syndrome (CRPS)

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)

Curvature of the Penis (Peyronie's Disease)

Cystic Fibrosis

Cysts (Overview)

Cytomegalovirus (CMV)

Decompression Sickness

Delusional Disorder

Depression Overview

Detached Retina

Developmental Dysplasia of the Hip

Deviated Septum

Diabetes Mellitus Overview

Diabetic Ketoacidosis

Diabetic Nephropathy

Diabetic Neuropathies

Dislocated Lens

Diverticulosis and Diverticulitis

Double Vision (Diplopia)

Drooping Eyelid (Ptosis)

Dry Eye Syndrome

Dysfunctional Uterine Bleeding

Encopresis (Fecal Soiling)

End-Stage Renal Disease

Endophthalmitis

Enlarged Prostate (Benign Prostatic Hyperplasia)

Epidemic Pleurodynia

Epidermoid Cyst

Epididymitis And Orchitis

Esophageal Cancer

Esophageal Rings And Webs

Esophageal Varices

Essential Tremor

Ewing's Sarcoma

Extragonadal Germ Cell Tumors

Eye Socket Fracture (Fracture Of The Orbit)

Fallopian Tube Cancer

Familial Dysautonomia

Farsightedness (Hyperopia)

Febrile Seizures

Fecal Incontinence

Female Infertility

Fifth Disease (Erythema Infectiosum)

Finger Dislocation

Foreign Body In Eye

Foreign Objects In The Ear

Fragile X Syndrome

Friction Blisters

Friedreich's Ataxia
Frostbite

Gallbladder and bile duct cancer

Gas (Flatulence)

Gastroenteritis In Adults

Gastroenteritis In Children

Gastroesophageal Reflux Disease (GERD)

Gastrointestinal Amebiasis

Gaucher Disease

Generalized Anxiety Disorder

Generalized Seizures (Grand Mal Seizures)

Gestational Diabetes

Giant Cell Arteritis (Temporal Arteritis)

Glioblastoma Multiforme

Glomerulonephritis

Granulomatosis with polyangiitis

Graves' Disease

Graves' Eye Disease (Graves' Ophthalmopathy)

Guillain-Barre Syndrome

Hay Fever (Allergic Rhinitis)

Head and Neck Cancer

Head Injury In Adults

Head Injury In Children

Headache Overview

Hearing Loss in Adults

Hearing Loss in Children

Heart Attack (Myocardial Infarction)

Heart Valve Problems

Heart Valve Replacement

Heat Stroke (Hyperthermia)

Hemochromatosis

Hemorrhagic Stroke

Hepatitis Overview

Hereditary-Patterned Baldness

High Blood Pressure (Hypertension)

High Cholesterol (Hypercholesterolemia)

Hives (Urticaria)

Hodgkin Lymphoma

Human Papilloma Virus (HPV)

Huntington's Disease (Chorea)

Hyperthyroidism

Hypoparathyroidism

Illness Anxiety Disorder

Immune Thrombocytopenic Purpura (ITP)

Impotence (Erectile Dysfunction)

Infectious Arthritis

Infectious Mononucleosis

Ingrown Toenail

Inguinal Hernia

Interstitial Cystitis

Intracranial Aneurysms

Iron Deficiency

Irritable Bowel Syndrome (IBS)

Jock Itch (Tinea Cruris)

Juvenile Arthritis

Kaposi's Sarcoma

Kawasaki Syndrome

Lactose Intolerance

Langerhans' Cell Histiocytosis (Histiocytosis X)

Lazy Eye (Amblyopia)

Leukemia (Overview)

Long QT Syndrome

Lung Cancer Overview

Lupus (Systemic Lupus Erythematosus)

Lymphoma Overview

Macular Degeneration

Major Depression

Male Infertility

Malignant Hyperthermia

Marfan Syndrome

Maturity Onset Diabetes of the Young (MODY)

Measles (Rubeola)

Meckel's Diverticulum

Medication Allergy

Melasma (Chloasma)

Meniere's Disease

Menopause And Perimenopause

Metastatic Brain Tumors

Mid-Menstrual Cycle Pain (Mittelschmerz)

Middle-Ear Infection (Otitis Media)

Mitral Valve Prolapse

Molar Pregnancy

Molluscum Contagiosum

Morton's Neuroma

MRSA Skin Infection

Multiple Myeloma

Multiple Sclerosis

Muscular Dystrophy

Myasthenia Gravis

Myelodysplastic Syndromes

Nabothian Cysts

Nearsightedness (Myopia)

Neurofibromatosis

Non-Hodgkin Lymphoma

Non-Small Cell Lung Cancer

Nosebleed (Epistaxis)

Obsessive-Compulsive Disorder (OCD)

Optic Nerve Swelling (Papilledema)

Osgood-Schlatter Disease

Paget's Disease of Bone

Painful Sexual Intercourse (Dyspareunia)

Pancreatic Cancer

Pancreatitis Overview

Panic Disorders

Parathyroid Cancer

Parkinson's Disease

Partial Seizures (Focal Seizures)

Pelvic Inflammatory Disease (PID)

Perforated Eardrum

Peripheral Arterial Disease

Peritonsillar Abscess

Pertussis (Whooping Cough)

Phenylketonuria (PKU)

Phimosis and Paraphimosis

Pinkeye (Conjunctivitis)

Pituitary Tumors

Pityriasis Rosea

Plague (Yersinia Pestis)

Plantar Fasciitis

Pleurisy And Pleural Effusion

Polyarteritis Nodosa

Polycystic Kidney Disease

Polycystic Ovary Syndrome

Polymyalgia Rheumatica

Post-Polio Syndrome

Post-Traumatic Stress Disorder

Posterior Cruciate Ligament (PCL) Injuries

Postpartum Depression

Preeclampsia And Eclampsia

Premature Ejaculation

Premenstrual Syndrome (PMS)

Prostate Cancer

Pseudogout (CPPD)

Psoriatic Arthritis

Pubic Lice Or Crab Lice

Raynaud's Phenomenon

Reactive Arthritis

Respiratory Syncytial Virus

Restless Legs Syndrome

Retinal Vessel Occlusion

Retinitis Pigmentosa

Retrobulbar Neuritis

Retrograde Ejaculation

Rhabdomyosarcoma

Rheumatoid Arthritis

Ringworm (Tinea)

Rocky Mountain Spotted Fever

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)

Shingles (Herpes Zoster)

Shoulder Dislocation

Shoulder Sprain

Sick Sinus Syndrome

Sickle Cell Anemia

Sjogren's Syndrome

Skin Tags (Acrochordon)

Sleepwalking and Sleep Terrors

Soft Tissue Sarcoma

Somatic Symptom Disorder

Sore Throat (Pharyngitis)

Spinal Cord Trauma

Spinal Cord Tumors

Sprain (Overview)

Squamous Cell Carcinoma of the Lung

Squamous Cell Carcinoma of the Skin

Stroke Overview

Styes And Chalazions

Subarachnoid Hemorrhage

Subdural Hematoma

Sun Allergy (Photosensitivity)

Sun-Damaged Skin

Superficial Thrombophlebitis

Swallowed Object

Swimmer's Ear (Otitis Externa)

Takayasu's Arteritis

Tay-Sachs Disease

Tear Duct Infection (Dacryocystitis)

Telogen Effluvium

Tennis Elbow (Lateral Epicondylitis)

Tension Headache

Testicular Cancer

Testicular Torsion

Throat Cancer (Larynx and Pharynx)

Thrombocytopenia

Thromboembolism (Deep Vein Thrombosis and Pulmonary Embolism)

Thrombotic Stroke

Tinea Versicolor

Toenail Fungus (Onychomycosis)

Torsional Deformity

Tourette Syndrome

Toxic Shock Syndrome

Transient Ischemic Attack (TIA)

Traumatic Dislocation of the Hip

Trigeminal Neuralgia (Tic Douloureux)

Type 1 Diabetes Mellitus

Type 2 Diabetes Mellitus

Ulcerative Colitis

Undescended Testicle

Urinary Incontinence

Urinary Tract Infection in Men

Urinary Tract Infection in Women

Uterine And Bladder Prolapse

Vaginal Atrophy (Atrophic Vaginitis)

Vaginal Discharge

Vaginal Yeast Infection

Vascular Birthmarks

Vasculitis Overview

Vitamin B12 Deficiency

Vocal Cord Disorders

Waldenström Macroglobulinemia

Wax Blockage Of The Ear Canal

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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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