|
Niemann–Pick disease ( ) is a group of inherited severe metabolic disorders that allows a certain kind of fat to accumulate in cells. The fat, sphingomyelin, accumulates in lysosomes (membrane-bound organelles in cells). The lysosomes normally transport material through and out of the cell. The prognosis is individual but the severe form is fatal in toddlerhood and the milder forms may even in some cases have a normal lifespan. This disease involves dysfunctional metabolism of sphingolipids, which are fats found in cell membranes, so it is a kind of sphingolipidosis. Sphingolipidoses, in turn, are included in the larger family of lysosomal storage diseases. ==Signs and symptoms== Symptoms are related to the organs in which sphingomyelin accumulates. Enlargement of the liver and spleen (hepatosplenomegaly) may cause reduced appetite, abdominal distension, and pain. Enlargement of the spleen (splenomegaly) may also cause low levels of platelets in the blood (thrombocytopenia). Accumulation of sphingomyelin in the central nervous system (including the cerebellum) results in unsteady gait (ataxia), slurring of speech (dysarthria), and difficulty in swallowing (dysphagia). Basal ganglia dysfunction causes abnormal posturing of the limbs, trunk, and face (dystonia). Upper brainstem disease results in impaired voluntary rapid eye movements (supranuclear gaze palsy). More widespread disease involving the cerebral cortex and subcortical structures causes gradual loss of intellectual abilities, causing dementia and seizures. Bones can also be affected: symptoms can include enlarged bone marrow cavities, thinned cortical bone, or a distortion of the hip bone called coxa vara. Sleep-related disorders, such as sleep inversion, sleepiness during the day and wakefulness at night, can occur. Gelastic cataplexy, the sudden loss of muscle tone when the patient laughs, is also seen. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Niemann–Pick disease」の詳細全文を読む スポンサード リンク
|