In-depth descriptions of the most common diseases, symptoms, procedures, and tests written by Harvard Medical School faculty members.

Table of Contents

• Abdominal Aortic Aneurysm
• Abdominal Adhesions
• Absence Seizures (Petit Mal Seizures)
• Achalasia
• ACL (Anterior Cruciate Ligament) Injuries
• Acne
• Acoustic Neuroma
• Sun-Damaged Skin
• Acute Pancreatitis
• Acute Prostatitis
• Acute Sinusitis
• Acute Bronchitis
• Adenocarcinoma of the Lung
• Attention-Deficit Hyperactivity Disorder (ADHD)
• Age Spots (Solar Lentigo, Liver Spots)
• Alcohol Dependence (Alcoholism)
• Alcohol Withdrawal
• Hay Fever (Allergic Rhinitis)
• Morton's Neuroma
• Alopecia Areata
• Amyotrophic Lateral Sclerosis (ALS)
• Altitude Sickness
• Alzheimer's Disease
• Amenorrhea
• Amyloidosis
• Anal Disorders
• Anaphylaxis
• Angina
• Ankle Fracture
• Ankle Sprain
• Ankylosing Spondylitis
• Anorexia Nervosa
• Antibiotic-Associated Diarrhea
• Antiphospholipid Antibody Syndrome
• Antisocial Personality Disorder
• Aplastic Anemia
• Appendicitis
• Arm Fracture
• Asthma
• Astigmatism
• Asymptomatic Bacteriuria
• Atherosclerosis
• Athlete's Foot (Tinea Pedis)
• Atrial Fibrillation
• Autism (Autism Spectrum Disorder)
• Back Pain
• Bacterial Vaginosis (Gardnerella Vaginitis)
• Balanitis
• Barium Enema
• Barotrauma
• Bartholin's Gland Cyst
• Basal Cell Carcinoma
• Bedsores (Decubitus Ulcers)
• Behcet's Disease
• Bells Palsy
• Bile Duct Diseases
• Biliary Colic
• Bipolar Disorder (Manic Depressive Illness or Manic Depression)
• Bladder Cancer
• Bladder Infection (Cystitis)
• Blepharitis
• Blisters (Overview)
• Body Lice
• Boils and Carbuncles
• Borderline Personality Disorder
• Botulism
• Bowel Obstruction
• Bradycardia
• Brain Tumor Overview
• Brain Abscess
• Breast Cancer
• Broken Jaw
• Broken Nose (Nasal Fracture)
• Bulimia
• Bunion
• Bursitis
• Campylobacteriosis
• Candidiasis
• Carbon Monoxide Poisoning
• Carcinoid tumors of the lung
• Cardiac Arrhythmias
• Cardiomyopathy
• Carpal Tunnel Syndrome
• Cataracts
• Celiac Disease (Non-Tropical Sprue)
• Cellulitis
• Cerebral Palsy
• Cervical Cancer
• Cervical Polyps
• Cervicitis
• Chemical Injury to the Eye
• Chickenpox (Varicella)
• Chlamydia
• Cholecystitis
• Chondromalacia
• Choroidal Melanoma
• Chronic Otitis Media, Cholesteatoma and Mastoiditis
• Chronic Fatigue Syndrome
• Chronic Hepatitis
• Chronic Laryngitis
• 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)
• Concussion
• Heart Failure
• Pinkeye (Conjunctivitis)
• Constipation and Impaction
• Contact Dermatitis
• Conversion Disorder
• Chronic Obstructive Pulmonary Disease (COPD)
• Corneal Abrasion
• Corns and Calluses
• Coronary Artery Disease
• Creutzfeldt-Jakob Disease (CJD)
• Crohn's Disease
• Crossed Eyes (Strabismus)
• Croup
• Cystic Fibrosis
• Cysts (Overview)
• Cytomegalovirus (CMV)
• Tear Duct Infection (Dacryocystitis)
• Dandruff
• Decompression Sickness
• Delusional Disorder
• Dementia
• Dermatofibroma
• Detached Retina
• Developmental Dysplasia of the Hip
• Deviated Septum
• Diabetic Neuropathies
• Diabetic Ketoacidosis
• Diabetic Nephropathy
• Diarrhea
• Dislocated Lens
• Diverticulosis and Diverticulitis
• Down Syndrome
• Dry Eye Syndrome
• Dysfunctional Uterine Bleeding
• Dyslexia
• Dysthymia
• Wax Blockage Of The Ear Canal
• Eczema
• Emphysema
• Encephalitis
• Encopresis (Fecal Soiling)
• Endocarditis
• Endometriosis
• Endophthalmitis
• End-Stage Renal Disease
• Enlarged Prostate (Benign Prostatic Hyperplasia)
• Bedwetting (Enuresis)
• Epidemic Pleurodynia
• Epididymitis And Orchitis
• Epiglottitis
• Epilepsy
• Esophageal Cancer
• Esophageal Rings And Webs
• Esophageal Varices
• Esophagitis
• Essential Tremor
• Ewing's Sarcoma
• Extragonadal Germ Cell Tumors
• Eye-Socket Fracture (Fracture Of The Orbit)
• Fallen Arch
• Fallopian Tube Cancer
• Familial Dysautonomia
• Farsightedness (Hyperopia)
• Febrile Seizures
• Fecal Incontinence
• Felon
• Female Infertility
• Fibroids
• Fibromyalgia
• Fifth Disease (Erythema Infectiosum)
• Finger Dislocation
• Food Allergy
• Food Poisoning
• Foot Sprain
• Foot Ulcers
• Foreign Body In Eye
• Foreign Objects In The Ear
• Fragile X Syndrome
• Friction Blisters
• Friedreich's Ataxia
• Frostbite
• Gallbladder and bile duct cancer
• Gallstones
• Gastritis
• Gastroenteritis In Adults
• Gastroenteritis In Children
• Gastroesophageal Reflux Disease (GERD)
• Gastrointestinal Amebiasis
• Generalized Anxiety Disorder
• Generalized Seizures (Grand Mal Seizures)
• Genital Herpes
• Genital Warts
• Gestational Diabetes
• Giant Cell Arteritis (Temporal Arteritis)
• Giardiasis
• Glaucoma
• Glomerulonephritis
• Gonorrhea
• Gout
• Graves’ Disease
• Graves’ Eye Disease (Graves’ Ophthalmopathy)
• Guillain-Barre Syndrome
• Hammertoe
• Head and Neck Cancer
• Head Lice
• Head Injury In Adults
• Head Injury In Children
• Heart Attack (Myocardial Infarction)
• Heart Murmur
• Heat Stroke (Hyperthermia)
• Hematuria
• Hemochromatosis
• Hemolytic Anemia
• Hemophilia
• Hemorrhagic Stroke
• Hemorrhoids
• Hepatitis A
• Hepatitis B
• Hepatitis C
• Hepatitis Overview
• Hereditary-Patterned Baldness
• Hernia
• Herniated Disk
• Hiatal Hernia
• High Blood Pressure (Hypertension)
• High Cholesterol (Hypercholesterolemia)
• Hip Fracture
• HIV/AIDS
• Hives (Urticaria)
• Human Papilloma Virus (HPV)
• Huntington's Disease (Chorea)
• Hydrocephalus
• Hyperkeratosis
• Hyperthyroidism
• Hypochondriasis
• Hypoglycemia
• Hypoparathyroidism
• Hypothyroidism
• Arthritis Associated With Inflammatory Bowel Disease
• Ichthyosis
• Immune Thrombocytopenic Purpura (ITP)
• Impetigo
• Infectious Arthritis
• Infectious Mononucleosis
• Flu (Influenza)
• Ingrown Toenail
• Inguinal Hernia
• Insomnia
• Interstitial Cystitis
• Iron Deficiency
• Irritable Bowel Syndrome (IBS)
• Jet Lag
• Jock Itch (Tinea Cruris)
• Juvenile Arthritis
• Kaposi's Sarcoma
• Kawasaki Syndrome
• Keloids
• Keratitis
• Kidney Stones
• Kidney Cancer
• Kidney Failure
• Kidney Transplant
• Knee Sprain
• Lactose Intolerance
• Lacunar Stroke
• Langerhans’ Cell Histiocytosis (Histiocytosis X)
• Large Cell Cancer of the Lung
• Laryngitis
• Latex Allergy
• Lazy Eye (Amblyopia)
• Lead Poisoning
• Leg Fracture
• Leg Strain
• Leukemia (Overview)
• Liver Cancer
• Lung Cancer Overview
• Lung Transplant
• Lupus (Systemic Lupus Erythematosus)
• Lyme Disease
• Lymphedema
• Lymphoma Overview
• Macular Degeneration
• Major Depression
• Malaria
• Male Infertility
• Malignant Hyperthermia
• Mesothelioma
• Marfan's Syndrome
• Measles (Rubeola)
• Meckel's Diverticulum
• Medication Allergy
• Melanoma
• Melasma (Chloasma)
• Meniere's Disease
• Meningitis
• Menopause And Perimenopause
• Migraine
• Miscarriage
• Mitral Valve Prolapse
• Molar Pregnancy
• Molluscum Contagiosum
• Multiple Myeloma
• Multiple Sclerosis
• Mumps
• Muscle Strain
• Muscular Dystrophy
• Myasthenia Gravis
• Myocarditis
• Myositis
• Nabothian Cysts
• Nail Trauma
• Narcolepsy
• Nasal Polyps
• Nearsightedness (Myopia)
• Nephrectomy
• Neuroblastoma
• Obesity
• Obsessive-Compulsive Disorder (OCD)
• Onycholysis
• Optic Nerve Swelling (Papilledema)
• Oral Cancer
• Osgood-Schlatter Disease
• Osteoarthritis
• Osteoporosis
• Osteosarcoma
• Middle-Ear Infection (Otitis Media)
• Ovarian Cancer
• Paget's Disease of Bone
• Pancreatic Cancer
• Panic Disorders
• Parathyroid Cancer
• Parkinson's Disease
• Paronychia
• Partial Seizures (Focal Seizures)
• Pelvic Inflammatory Disease (PID)
• Peptic Ulcer
• Perforated Eardrum
• Pericarditis
• Peripheral Arterial Disease
• Peritonsillar Abscess
• Vitamin B12 Deficiency
• Curvature of the Penis (Peyronie's Disease)
• Phenylketonuria (PKU)
• Phimosis and Paraphimosis
• Phobia
• Pituitary Tumors
• Pityriasis Rosea
• Plantar Fasciitis
• Pleurisy And Pleural Effusion
• Pneumoconiosis
• Pneumonia
• Pneumothorax
• Polio
• Polyarteritis Nodosa
• Polychondritis
• Polycystic Ovary Syndrome
• Polymyalgia Rheumatica
• Posterior Cruciate Ligament (PCL) Injuries
• Postpartum Depression
• Post-Polio Syndrome
• Post-Traumatic Stress Disorder
• Preeclampsia And Eclampsia
• Premenstrual Syndrome (PMS)
• Presbyopia
• Priapism
• Prostate Cancer
• Pseudogout (CPPD)
• Psoriasis
• Psoriatic Arthritis
• Pubic Lice Or Crab Lice
• Pyelonephritis
• Raynaud's Phenomenon
• Rectocele
• Complex Regional Pain Syndrome (CRPS)
• Reactive Arthritis
• Respiratory Syncytial Virus
• Restless Legs Syndrome
• Retinal Vessel Occlusion
• Retinitis Pigmentosa
• Retinoblastoma
• Retinopathy
• Retrobulbar Neuritis
• Retrograde Ejaculation
• Reye Syndrome
• Rhabdomyosarcoma
• Rheumatoid Arthritis
• Ringworm (Tinea)
• Rocky Mountain Spotted Fever
• Rosacea
• Rotator Cuff Injury
• Salivary Gland Disorders
• Sarcoidosis
• Scabies
• Scarlet Fever
• Schizophrenia
• Schizotypal Personality Disorder
• Sciatica
• Scleritis
• Scleroderma
• Scoliosis
• Sebaceous Cysts
• Seborrheic Dermatitis
• Seborrheic Keratoses
• Secondary Hypertension
• Substance Abuse (Depressants or Sedative-Hypnotic Drugs)
• Seizure Overview
• Sexually Transmitted Diseases (Overview)
• Shigellosis
• Shingles (Herpes Zoster)
• Shin Splints
• Shoulder Dislocation
• Shoulder Sprain
• Sickle Cell Anemia
• Sjogren's Syndrome
• Skin Tags (Acrochordon)
• Sleep Apnea
• Sleepwalking and Sleep Terrors
• Small Cell Lung Cancer
• Smallpox
• Soft Tissue Sarcoma
• Somatization Disorder
• Spider Veins
• Spina Bifida
• Spinal Cord Trauma
• Spinal Cord Tumors
• Sprain (Overview)
• Squamous Cell Carcinoma of the Skin
• Squamous cell carcinoma of the lung
• Stomach Cancer
• Stroke Overview
• Stuttering
• Styes And Chalazions
• Subarachnoid Hemorrhage
• Subdural Hematoma
• Sun Allergy (Photosensitivity)
• Swallowed Object
• Swimmer's Ear (Otitis Externa)
• Syphilis
• Tachycardia
• Takayasu's Arteritis
• Tay-Sachs Disease
• Telogen Effluvium
• Tendonitis
• Tennis Elbow (Lateral Epicondylitis)
• Tension Headache
• Testicular Cancer
• Testicular Torsion
• Tetanus
• Throat Cancer (larynx and pharynx)
• Thrombocytopenia
• Thromboembolism (Deep Vein Thrombosis and Pulmonary Embolism)
• Superficial Thrombophlebitis
• Thrombotic Stroke
• Thyroid Cancer
• Thyroidectomy
• Tick Bites
• Tics
• Tinea Versicolor
• Tinnitus
• Toenail Fungus (Onychomycosis)
• Torn Meniscus
• Torsional Deformity
• Tourette Syndrome (Tourette Disorder)
• Toxic Shock Syndrome
• Toxoplasmosis
• Transient Ischemic Attack (TIA)
• Traumatic Dislocation of the Hip
• Traveler's Diarrhea
• Trichomoniasis
• Trigeminal Neuralgia (Tic Douloureux)
• Tropical Sprue
• Tuberculosis
• Type 1 Diabetes Mellitus
• Type 2 Diabetes Mellitus
• Ulcerative Colitis
• Undescended Testicle
• Urethritis
• Urinary Incontinence
• Urinary Tract Infection in Men
• Uterine And Bladder Prolapse
• Urinary Tract Infection in Women
• Uveitis
• Vaginal Atrophy (Atrophic Vaginitis)
• Vaginal Cancer
• Vaginal Yeast Infection
• Vaginitis
• Varicose Veins
• Vascular Birthmarks
• Vasculitis Overview
• Vertigo
• Vitiligo
• Vocal Cord Disorders
• Vulvar Cancer
• Warts
• Wegener's Granulomatosis
• Wilms’ Tumor
• Wrist Sprain
• Yaws
• Plague (Yersinia Pestis)
• Uterine Cancer
• Polycystic Kidney Disease
• Intracranial Aneurysms
• Gaucher Disease
• Sick Sinus Syndrome
• Long QT Syndrome
• Maturity Onset Diabetes of the Young (MODY)
• Epidermoid Cyst
• Adrenocortical Carcinoma
• Acute Lymphocytic Leukemia (ALL) in Adults
• Anal Cancer
• Chondrosarcoma
• Chronic Lymphocytic Leukemia (CLL)
• Glioblastoma Multiforme
• Hodgkin Lymphoma
• Metastatic Brain Tumors
• Myelodysplastic Syndromes
• Non-Hodgkin Lymphoma
• Waldenström Macroglobulinemia
• Acute Myeloid Leukemia (AML)
• Neurofibromatosis
• Non-Small Cell Lung Cancer
• Acute Lymphocytic Leukemia (ALL) in Children
• Pertussis (Whooping Cough)
• Aging Overview
• Pre-Diabetes
• Abortion (Termination Of Pregnancy)
• Allergy Shots (Allergen Immunotherapy)
• Angioplasty
• Arthroscopic Surgery
• Biofeedback
• Biopsy
• Bone Marrow Transplant
• Bone Scan
• Bronchoscopy
• Caesarean Section
• Cardiac Catheterization
• Chemotherapy
• Cholecystectomy
• Colonoscopy
• Colposcopy
• Computed Tomography (CT)
• Corneal Transplant
• Cystoscopy
• Digital Rectal Exam
• Electrocardiogram (EKG)
• Electroencephalogram (EEG)
• Endoscopy
• Fecal Occult Blood Test
• Heart-Lung Transplant
• Heart Transplant
• Heart Valve Replacement
• Hernia Repair
• Hysterectomy
• Immunotherapy
• Implantable Cardioverter Defibrillator (ICD)
• LASIK
• Magnetic Resonance Imaging (MRI)
• Mammography
• Pacemaker
• Pap Test (Papanicolaou Smear)
• Positron Emission Tomography (PET Scan)
• Pneumonectomy
• Prostate-Specific Antigen Blood Test (PSA Test)
• Radiation Therapy
• Radionuclide Scanning
• Sigmoidoscopy
• Sutures
• Ultrasound
• Urinary Catheterization
• Vasectomy
• X-Rays
• Coronary Artery Bypass Surgery
• Abdominal Ultrasound
• Foot X-Ray
• Large Core Needle Biopsy of the Breast
• Thyroid Nuclear Medicine Tests (Thyroid Scan and Uptake)
• Blood Testing
• Acupuncture
• Anal Itch (Pruritus Ani)
• Black Eye
• Double Vision (Diplopia)
• Drooping Eyelid (Ptosis)
• Dry Skin
• Painful Sexual Intercourse (Dyspareunia)
• Dysuria
• Earache
• Edema
• Fever
• Gas (Flatulence)
• Hair Loss
• Hearing Loss in Adults
• Hearing Loss in Children
• Heart Valve Problems
• Heel Pain
• Hirsutism
• Hot Flashes
• Impotence (Erectile Dysfunction)
• Mid-Menstrual Cycle Pain (Mittelschmerz)
• Moles (Nevi)
• Nausea
• Nosebleed (Epistaxis)
• Pain
• Sore Throat (Pharyngitis)
• Premature Ejaculation
• Rash
• Vaginal Discharge
• Abdominal CT Scan (Computed Tomography Scan)
• Amniocentesis
• Anoscopy
• Arterial Blood Flow Studies of the Legs (Segmental Doppler Pressures)
• Back X-Rays (Spine X-Rays)
• Barium Enema
• Biopsy of the Prostate and Transrectal Ultrasound
• Bone Density Test
• Bone Marrow Biopsy
• Breast Ultrasound
• Carotid Ultrasound (Carotid Doppler)
• Chest X-Ray
• Chorionic Villus Sampling
• Colposcopy and Cervical Biopsy
• Computed Tomography (CT Scan) for Back Problems
• Cystourethrogram
• Echocardiogram
• Electromyography
• Electrophysiological Testing of the Heart
• Endometrial Biopsy
• Endoscopic Retrograde Cholangiopancreatography (ERCP)
• Screening for Birth Defects in Early Pregnancy (Combined Test, Integrated Test, and Quadruple Test)
• Excisional Biopsy of the Breast
• Exercise Stress Test
• Fetal Ultrasound
• Fine-Needle Aspiration (FNA) of the breast
• Flourescein Angiography (Test for Diabetic Retinopathy)
• Holter Monitor and Event Monitor
• Hysterosalpingogram
• Hysteroscopy
• Kidney Biopsy
• Laparoscopy and Laparoscopic Surgery
• Liver Biopsy
• Venous Ultrasound of the Legs (Lower Extremity Doppler)
• Lymph Node Biopsy
• Mediastinoscopy
• Myelography (Myelogram)
• Oxygen Saturation Test
• Pelvic Ultrasound and Transvaginal Ultrasound
• Percutaneous Transhepatic Cholangiography (PTCA)
• Pulmonary Function Testing
• Rapid Strep Test
• Scratch Test for Allergies
• Skin Biopsy
• Snellen Test for Visual Acuity
• Lumbar Puncture (or Spinal Tap)
• Sputum Evaluation (and Sputum Induction)
• Stereotactic Biopsy of the Breast
• Testing for Vaginitis (Yeast Infections, Trichomonas, and Gardnerella)
• Pleural Fluid Sampling (or Thoracentesis)
• Throat Culture
• Tonometry
• TB (Tuberculosis) Skin Test
• Upper Endoscopy (Esophagogastroduodenoscopy or "EGD")
• Barium Swallow (Upper Gastrointestinal Series or "Upper GI Series")
• Urinalysis
• Ventilation-Perfusion Scan or "V-Q Scan"
• Video-Assisted Thoracic Surgery
• Wire Localization Biopsy of the Breast