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• 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.