Nightmare disorder is a sleep disorder characterized by recurrent, vivid, and distressing dreams that typically involve threats to survival, safety, or physical integrity. These nightmares usually occur during rapid eye movement sleep and often cause abrupt awakenings with clear recall of the dream content. Nightmare disorder can affect both children and adults and may interfere with sleep quality, emotional well-being, …

Niemann-Pick disease is a group of rare inherited metabolic disorders that affect the body’s ability to break down and transport fats, particularly cholesterol and sphingomyelin, within cells. As a result, harmful amounts of these substances accumulate in organs such as the liver, spleen, lungs, bone marrow, and brain. The disease typically begins in infancy or childhood, although some forms may …

Peripheral neuropathy is an umbrella term for nerve diseases that affect a specific subdivision of your nervous system. Many different conditions can cause peripheral neuropathy, which means a wide range of symptoms is also possible. Peripheral neuropathy can also affect different body parts, depending on how and why it happens. What this name means The term “peripheral” is from the …

Neurofibroma is a benign tumor that develops from nerve tissue and is made up of a mixture of nerve cells, connective tissue, and supporting cells. These tumors commonly occur on or under the skin but may also develop along deeper nerves in the body. Neurofibromas can appear as isolated growths or as part of a genetic condition known as neurofibromatosis. …

Neuroendocrine tumors are a diverse group of cancers that develop from neuroendocrine cells, which have traits of both nerve cells and hormone-producing cells. These cells are found throughout the body, especially in organs such as the gastrointestinal tract, pancreas, and lungs. Neuroendocrine tumors may grow slowly or aggressively and can be functional, producing excess hormones, or nonfunctional, producing no hormones …

Schwannomatosis is a rare genetic disorder characterized by the development of multiple schwannomas, which are typically benign tumors that grow from Schwann cells surrounding peripheral nerves. Unlike neurofibromatosis type 2, schwannomatosis usually does not involve tumors on the hearing nerves and does not commonly cause hearing loss. Schwannomatosis often appears in adulthood and can cause chronic pain due to nerve …

Schwannoma is a usually benign tumor that develops from Schwann cells, which are responsible for forming the protective covering around nerves called the myelin sheath. These tumors can occur along any peripheral nerve in the body but are most commonly found in the head, neck, and extremities. A well-known type is vestibular schwannoma, which affects the nerve responsible for hearing …

Postherpetic neuralgia (PHN) is a complication of shingles infection (also called herpes zoster). Shingles is caused by the reactivation of the varicella-zoster virus, which is the same virus that causes chickenpox. Shingles causes a painful, blistering rash and other symptoms. The rash most commonly occurs in a band pattern on one side of your body, usually on your trunk (central core of …

Nephrotic syndrome is a kidney disorder characterized by excessive loss of protein in the urine due to damage to the filtering units of the kidneys, known as glomeruli. This loss of protein leads to low levels of protein in the blood and causes fluid to leak into body tissues. Nephrotic syndrome can occur in both children and adults and may …

Nephrogenic systemic fibrosis is a rare but serious condition characterized by thickening and hardening of the skin and connective tissues. It occurs almost exclusively in people with severe kidney dysfunction, particularly those with advanced chronic kidney disease or acute kidney failure. The condition has been strongly associated with exposure to certain gadolinium-based contrast agents used during magnetic resonance imaging scans. …