Niemann–Pick disease is a group of inherited, severe metabolic disorders in which sphingomyelin accumulates in lysosomes in cells. The lysosomes normally transport material through and out of the cell.
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.
The prognosis is individual, but the severe form is fatal in toddlerhood and, in some cases, patients with the milder forms may have normal lifespans.
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 also may be affected: symptoms may 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, may occur.
Niemann–Pick disease has an autosomal recessive pattern of inheritance
- Niemann–Pick disease, SMPD1-associated, which includes types A and B
- Niemann–Pick disease type A: classic infantile
- Niemann–Pick disease type B: visceral
- Niemann–Pick disease, type C: subacute/juvenile, includes types C1 (95% of type C) and C2.
No specific treatment is known for type A, but symptoms are treated.
See reference for more information.
Adapted from Wikipedia, the free encyclopedia. Internet. Accessed on March 9, 2017.