Health Library

Articles In This Section

• A to Z: Nystagmus

  Learn more about this eye problem.

• A to Z: Obesity, Morbid

  Learn about causes and complications of obesity and morbid obesity.

• A to Z: Obstructive Sleep Apnea

  Learn about this common sleep disorder, where a blockage of the airway during sleep can cause someone to temporarily stop breathing.

• A to Z: Omphalitis

  Learn about bacterial infections and conditions that affect newborn babies.

• A to Z: Open Wound, Cheek

  Learn more about cheek wounds and how they're treated.

• A to Z: Open Wound, Ear

  Learn about ear wounds and how they're treated.

• A to Z: Open Wound, Elbow

  Learn more about elbow wounds and how they're treated.

• A to Z: Open Wound, Face

  Learn about face wounds and how they're treated.

• A to Z: Open Wound, Finger

  Learn more about finger wounds and how they're treated.

• A to Z: Open Wound, Foot

  Learn more about foot wounds and how they're treated.

• A to Z: Open Wound, Forearm

  Learn more about forearm wounds and how they're treated.

• A to Z: Open Wound, Forehead

  Learn more about forehead wounds and how they're treated.

• A to Z: Open Wound, Gum

  Learn more about gum wounds and how they're treated.

• A to Z: Open Wound, Hand

  Learn more about hand wounds and how they're treated.

• A to Z: Open Wound, Head

  Learn more about head wounds and how they're treated.

• A to Z: Open Wound, Hip and Thigh

  Learn more about wounds of this hip or thigh and how they're treated.

• A to Z: Open Wound, Jaw

  Learn more about jaw wounds and how they're treated.

• A to Z: Open Wound, Knee/Leg/Ankle

  Learn more about knee, leg, and ankle wounds and how they're treated.

• A to Z: Open Wound, Lip

  Learn more about lip wounds and how they're treated.

• A to Z: Open Wound, Mouth

  Learn more about mouth wounds and how they're treated.

• A to Z: Open Wound, Nose

  Learn more about nose wounds and how they're treated.

• A to Z: Open Wound, Scalp

  Learn more about scalp wounds and how they're treated.

• A to Z: Mononucleosis

  Learn more about mononucleosis, an infection caused by the Epstein-Barr virus (EBV) with flu-like symptoms.

• A to Z: Mucopolysaccharidosis Type II

  Mucopolysaccharidosis type II, or Hunter syndrome, is a rare genetic disorder that affects mostly males.

• A to Z: Multiple Sclerosis (MS)

  Learn about about multiple sclerosis (MS), a chronic disease affecting the central nervous system.

• A to Z: Myalgia

  Learn about causes of muscle pain and conditions that affect muscles and muscle groups.

• A to Z: Myasthenia Gravis (MG)

  Learn about myasthenia gravis, an autoimmune disease that causes weakness in the voluntary muscles.

• A to Z: Myelomeningocele

  Learn about birth defects and conditions that affect the spinal cord and spinal column.

• A to Z: Myoclonus

  Learn more about the central nervous system and symptoms of nervous system disorders.

• A to Z: Myopia

  Myopia is nearsightedness, a common condition in which someone can see things that are close clearly, but things that are farther away appear blurry.

• A to Z: Myositis

  Learn about causes of muscle weakness and conditions that affect muscles and muscle tissue.

• A to Z: Myringitis, Bullous

  Learn about bullous myringitis, an infection of the tympanic membrane (eardrum).

• A to Z: Myringitis, Infectious

  Learn about bullous myringitis, an infection of the tympanic membrane (eardrum).

• A to Z: MSSA

  Learn about causes and complications of skin infections.

• A to Z Symptom: Nausea

  Nausea (stomach upset or feeling queasy) can be caused by many things. Often, it can be managed at home with treatment to prevent dehydration.

• A to Z: Necrotizing Enterocolitis

  Necrotizing enterocolitis (NEC) is a serious intestinal problem where tissue in a newborn's colon dies off. Babies with necrotizing enterocolitis need medical care right away.

• A to Z: Necrotizing Respiratory Granulomatosis

  See: Granulomatosis With Polyangiitis (GPA).

• A to Z: Nephrotic Syndrome

  Learn about conditions that affect the kidneys and urinary tract.

• A to Z: Neurofibromatosis

  Learn more about neurofibromatosis (NF), which can cause tumors to grow, including how it's treated.

• A to Z: Neurogenic Bladder

  The term neurogenic bladder refers to a bladder that doesn't function properly because of nervous damage.

• A to Z: Neurosis

  See: Mental Disorder, Non-psychotic.

• A to Z: Nonunion of Fracture

  In this condition, a broken bone does not heal completely and needs advanced treatment. Learn more.

• A to Z: Norovirus

  Learn about viral infections and conditions that affect the stomach and digestive system.

• A to Z: Li-Fraumeni Syndrome

  This genetic condition makes a person more likely to get cancer during his or her lifetime. Learn more here.

• A to Z: Lipoma

  A lipoma is a non-cancerous mass of fat cells that grows under the skin.

• A to Z: Lyme Disease

  Lyme disease is a bacterial infection spread through the bite of deer ticks.

• A to Z: Lymphadenitis

  Learn about bacterial infections and problems of the lymphatic system.

• A to Z: Lymphangioma Circumscriptum

  Learn about congenital defects and conditions that affect the lymphatic system.

• A to Z Symptom: Malaise and Fatigue

  Malaise and fatigue are common symptoms of many ailments.

• A to Z: MRSA

  Learn about causes and complications of skin infections.

• A to Z: Marcus Gunn Syndrome

  Marcus Gunn syndrome is a congenital condition where a drooping eyelid briefly opens wider and appears to wink when the jaw is moved.

• A to Z: Meatal Stenosis

  The meatus is the opening in the penis where urine (pee) comes out. In meatal stenosis, the meatus is too small.

• A to Z: Meibomian Cyst

  A meibomian cyst, or chalazion, is a lump on the inner side of the eyelid. It occurs when one of the small oil glands becomes blocked.

• A to Z: Meningitis, Bacterial

  Learn about this rare but serious condition in which bacteria invade the membranes around the brain and spinal cord.

• A to Z: Meningitis, Viral

  Sometimes viruses can spread to the meninges, the membrane around the brain and spinal cord, and cause more severe illness. Learn about it here.

• A to Z: Mental Disorder, Non-psychotic

  Learn about types of mental disorders and conditions that affect thinking and behavior.

• A to Z: Metabolic Syndrome

  Metabolic syndrome is a group of separate health problems that often happen together in a person.

• A to Z: Microcephaly

  Microcephaly is a rare condition in which a child's brain doesn't fully develop, resulting in an abnormally small head size.

• A to Z: Migraine

  A migraine is a recurring headache that often causes nausea, dizziness, and sensitivity to light, sound, or smell.

• A to Z: Migraine, Without Aura

  A migraine without aura is a migraine headache that happens without previous warning signs (auras).

• A to Z: Mitochondrial Disorder

  Mitochondrial disorders affect the function of mitochondria, tiny structures within the body's cells that turn sugar and oxygen into the energy the cells need to do their jobs.

• A to Z: Molluscum Contagiosum

  Molluscum contagiosum is a common wart-like viral skin infection that goes away on its own over time.

• A to Z: Mononeuritis Multiplex

  Learn about complications of neurologic disorders and conditions that can affect the peripheral nerves.

• A to Z: Iritis

  Learn more about conditions of the eyes and factors that may contribute to vision loss.

• A to Z: Iron-Deficiency Anemia

  Iron-deficiency anemia occurs when there aren't enough healthy red blood cells in the bloodstream to carry oxygen to the body's tissues.

• A to Z: Irritable Bowel Syndrome

  Irritable bowel syndrome (IBS) is a common intestinal disorder that can cause cramps, gas, bloating, diarrhea, and constipation. It is sometimes called a "nervous stomach" or a "spastic colon."

• A to Z: Jaundice

  Learn about jaundice, when the skin and whites of the eyes appear yellow due to excess bilirubin in the blood.

• A to Z: Juvenile Idiopathic Arthritis (JIA)

  Learn about juvenile idiopathic arthritis, which usually occurs in kids and teens under age 17.

• A to Z: Juvenile Myoclonic Epilepsy

  Kids and teens with juvenile myoclonic epilepsy (JME) have multiple seizures that usually start around puberty and continue into adulthood unless the seizures are controlled by medicine.

• A to Z: Juvenile Rheumatoid Arthritis (JRA)

  See: Juvenile Idiopathic Arthritis (JIA).

• A to Z: Kawasaki Disease

  Learn about Kawasaki disease, an illness that involves the skin, mouth, and lymph nodes.

• A to Z: Keloids

  Learn about complications of wound healing and conditions that affect the skin.

• A to Z: Kidney Disease

  Kidney disease is when there's a problem with the kidneys and they can't do a good job of filtering waste.

• A to Z: Kidney Failure

  When the kidneys stop working, they can't help the body remove waste. Learn more about this condition and how doctors treat it.

• A to Z: Kidney Stones

  Learn more about diseases and conditions of the blood and kidneys.

• A to Z: Kleine-Levin Syndrome

  Learn about this rare disorder that primarily affects adolescent males.

• A to Z: Klinefelter Syndrome

  Learn about genetic disorders and conditions that can affect social and sexual development.

• A to Z: Kohler’s Disease

  Kohler's disease is a rare cause of foot pain that develops from temporary changes in bones in the feet as kids grow.

• A to Z: Lactose Intolerance

  Lactose intolerance happens because the body has trouble digesting a kind of sugar that's in milk products.

• A to Z: Hypoglycemia

  Learn more about hypoglycemia, a condition where glucose levels drop below normal.

• A to Z: Hyponatremia

  Hyponatremia is an abnormally low level of sodium in the blood.

• A to Z: Hypoplastic Left Heart Syndrome

  Learn about hypoplastic left heart syndrome, a rare and serious defect of the heart.

• A to Z: Hyposmolality

  Learn about metabolic conditions and conditions that can affect fluid and electrolyte levels in the blood.

• A to Z: Hypospadias

  Hypospadias is a birth defect in which the tube that carries urine out of the body, called the urethra, opens on the underside of the penis.

• A to Z: Hypothermia

  Hypothermia is a medical emergency resulting from dangerously low body temperature.

• A to Z: Hypothyroidism

  Hypothyroidism is when the thyroid gland doesn't send enough thyroid hormone into the blood.

• A to Z: Idiopathic Thrombocytopenic Purpura

  Learn about immune system responses and conditions that can affect the blood.

• A to Z: Ileus

  Learn about intestinal blockages and conditions that affect the digestive tract.

• A to Z: Immune Thrombocytopenic Purpura

  See: Idiopathic Thrombocytopenic Purpura.

• A to Z: Impacted Cerumen

  Learn more about imnpacted earwax build-up, which can cause temporary hearing loss and ear pain.

• A to Z: Impetigo

  Impetigo is a contagious skin infection caused by bacteria.

• A to Z: Infection, Skin

  A skin infection is a condition where bacteria or other germs enter the skin through a wound and spread, causing pain, swelling, and discoloration.

• A to Z: Inflammatory Bowel Disease

  Inflammatory bowel disease is a term medical people use for two diseases of the intestines, Crohn's disease and ulcerative colitis, that cause problems in the intestine.

• A to Z: Influenza (Flu)

  Learn more about influenza (the flu), a highly contagious viral infection of the respiratory tract.

• A to Z: Insect Bites/Stings, Non-Venomous

  Bites from non-venomous insects are the result of an insect attempting to feed upon a person's blood. Non-venomous means the insect does not inject poisons through its bite.

• A to Z: Insect Bites/Stings, Venomous

  Venomous insects bite or sting people as a way to defend themselves. They inject a poison (venom) into a person through their mouth or stinger which causes a reaction.

• A to Z: Interrupted Aortic Arch

  Read about this condition in which the aorta has developed in a way that divides it into two parts and interrupts the proper flow of blood.

• A to Z: Interventricular Septal Defect

  Learn about congenital heart defects and conditions that affect the heart and circulatory system.

• A to Z: Intestinal Malabsorption

  Learn about gastrointestinal problems and conditions that affect the digestive system.

• A to Z: Intestinal Malrotation

  Malrotation is twisting of the bowel that happens when a baby's intestines don't develop properly in the uterus. It can be a medical emergency.

• A to Z: Intracerebral Hemorrhage

  See: Hemorrhage, Intracerebral.

• A to Z: Intussusception

  Intussusception is a problem with the intestine in which one portion of the bowel slides into the next.

• A to Z: Iridocyclitis

  Learn more about conditions of the eyes and factors that may contribute to vision loss.

• A to Z: Hernia, Bilateral

  A bilateral hernia is an opening or weakness in the abdominal wall on both sides of the groin. Learn about it here.

• A to Z: Hernia, Epigastric

  Learn about hernias and conditions that affect the abdomen and abdominal muscles.

• A to Z: Hernia, Hiatal

  Learn about hernias and conditions that affect the stomach, esophagus, and upper gastrointestinal tract.

• A to Z: Hernia, Incisional

  Learn about hernias and potential complications of abdominal surgery.

• A to Z: Hernia, Inguinal

  Learn about hernias and conditions that affect the lower abdomen and reproductive organs.

• A to Z: Hernia, Umbilical

  Learn about hernias and conditions that affect the abdomen and bellybutton.

• A to Z: Herpangina

  Learn more about viral infections and conditions that affect the mouth and throat.

• A to Z: Herpes Simplex 1

  Learn about viral infections, types of herpes, and conditions that affect the mouth and face.

• A to Z: Herpes Zoster

  Learn about viral infections and causes of skin conditions.

• A to Z: Hidradenitis

  In this condition, which often begins during the teen years, lumps form under the skin in areas like the armpit or groin. Learn more here.

• A to Z: Hirschsprung Disease

  Learn about Hirschsprung disease, a birth defect that prevents a child from passing bowel movements.

• A to Z: Hives

  Learn about urticaria, the red raised bumps or welts on the skin that are commonly called hives.

• A to Z: Hunter Syndrome

  See: Mucopolysaccharidosis (Hunter Syndrome).

• A to Z: Hydrocele

  A hydrocele is a collection of fluid around the testicle within the scrotum.

• A to Z: Hydrocephalus

  Hydrocephalus (sometimes called "water on the brain") is a brain condition that happens when cerebral spinal fluid (CSF) is unable to drain from the brain.

• A to Z: Hydromyelia

  Learn about the central nervous system and conditions that can affect the spinal cord.

• A to Z: Hydronephrosis

  Learn more about hydronephrosis (swollen kidney) in children.

• A to Z: Hyperkalemia

  Learn more about diseases and conditions of the blood and kidneys.

• A to Z: Hyperopia

  Hyperopia is farsightedness, a common condition in which someone can see things in the distance clearly, but things that are closer appear blurry.

• A to Z: Hypertension, Intracranial

  Learn about causes of vision loss and conditions that can affect the brain and nervous system.

• A to Z: Hypertension, Primary

  Learn about types of high blood pressure and conditions that can affect the heart and blood vessels.

• A to Z: Hypertension, Pulmonary

  Learn about types of high blood pressure and conditions that can affect the lungs and heart.

• A to Z: Hypertriglyceridemia

  In this common condition, there is a high level of fats called triglycerides in the blood. Learn how this is related to diet, lifestyle, and heart disease here.

• A to Z: Hypertrophy, Tonsillar (Enlarged Tonsils)

  Tonsillar hypertrophy, or enlarged tonsils, can happen due to an ongoing (chronic) condition or a temporary effect of an infection.

• A to Z: Hyphema

  Hyphema is a condition that happens when blood collects in the front part of the eye.

• A to Z: Hypogammaglobulinemia

  Learn about complications of white blood cell deficiencies and conditions that affect the immune system.

• A to Z: Gingivostomatitis, Herpetic

  Herpetic gingivostomatitis is a contagious mouth infection caused by herpes simplex virus type 1 (HSV-1). It most often occurs in young children and is usually the first exposure a child has to the herpes virus (which is also responsible for cold sores and fever blisters).

• A to Z: Glomerulonephritis

  Glomerulonephritis is an inflammation of the glomeruli, the parts of the filtering units (nephrons) of the kidney.

• A to Z: Glycogenosis

  Glycogenosis is a broad term for 11 different disorders that cause the abnormal use and storage of glycogen in the body's tissues.

• A to Z: Granulomatosis with Polyangiitis (GPA)

  Learn about granulomatosis with polyangiitis (GPA), an uncommon autoimmune disorder that causes inflammation of the blood vessels.

• A to Z: Graves Disease

  Graves disease is a condition where the body's immune system causes the thyroid gland to make more thyroid hormones than it should.

• A to Z: Growth Disorder

  Growth disorders are medical problems that stop kids from growing taller or gaining weight as they should.

• A to Z Symptom: Headache

  Headaches are common in kids and teens, and can have a wide range of causes. Most can be managed at home.

• A to Z: Hand, Foot, and Mouth Disease

  Hand, Foot, and Mouth disease is a common contagious illness caused by viruses from the enterovirus family, most commonly the coxsackievirus.

• A to Z: Hashimoto’s Thyroiditis

  Hashimoto's thyroiditis is a chronic (ongoing) condition where the body's immune system attacks the thyroid, a gland in the neck that makes thyroid hormone.

• A to Z: Hay Fever

  See: Rhinitis, Allergic.

• A to Z: Hearing Loss, Conductive

  Learn about causes of hearing loss and conditions that can affect the outer ear and middle ear.

• A to Z: Hearing Loss, Mixed

  Learn about causes of hearing loss and conditions that can affect the ear and auditory nerve.

• A to Z: Hearing Loss, Neural

  Learn about causes of hearing loss and conditions that can affect the auditory nerve.

• A to Z: Hearing Loss, Perceptive

  See: Hearing Loss, Sensorineural.

• A to Z: Hearing Loss, Sensorineural

  Learn about causes of hearing loss and conditions that can affect the inner ear and auditory nerve.

• A to Z: Hemangioma

  Learn more about hemangiomas, common birthmarks in infants.

• A to Z: Hematemesis

  Learn more about diseases and conditions of the stomach and digestive system.

• A to Z: Hematuria (Blood in Urine)

  Learn more about hematuria (blood in urine) and how it's treated.

• A to Z: Hemiplegia

  Learn about congenital disorders and conditions that affect the brain and central nervous system.

• A to Z: Hemophilia A (Factor VIII Deficiency)

  In factor VIII deficiency (hemophilia A), the body doesn't make enough factor VIII (factor 8), one of the substances the body needs to form a clot.

• A to Z: Hemophilia B (Factor IX Deficiency)

  In hemophilia B (factor IX deficiency), the body doesn't make enough factor IX (factor 9), one of the substances the body needs to form a clot.