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Niemann-Pick disease refers to a category of genetic metabolic disorders known as lipid storage diseases. This condition is characterized as a sphingolipidosis caused by insufficient sphingomyelinase activity, which results in the accumulation of sphingomyelin in reticuloendothelial cells.

Morphologically, Niemann – Pick cells range from 20 to 100 μm in diameter and contain numerous sharply defined small vacuoles in the cytoplasm, imparting a foamy, mulberry-like or soap-suds appearance (due to the accumulation of sphingomyelin in the cytoplasm).

There are three common forms of the disease:

•              Type A

•              Type B

•              Type C

Niemann-Pick disease types A and B are both attributable to mutations in the SMPD1 gene. This condition is frequently referred to as acid sphingomyelinase deficiency (ASMD).

Type A — recognized as the most severe manifestation — commences during infancy. Manifestations include hepatomegaly, significant neurological impairment, and progressive nerve degeneration. Currently, there exists no therapeutic intervention. The majority of affected children do not survive beyond a few years of life.

Type B — occasionally termed juvenile-onset Niemann-Pick disease — typically initiates at a later stage in childhood. Manifestations encompass neuropathic pain, ambulation difficulties, visual disturbances, and hepatosplenomegaly. Most individuals with type B reach adulthood; however, hepatic and pulmonary issues tend to exacerbate progressively.

Niemann-Pick disease type C is a genetic disorder resulting from mutations in the NPC1 and NPC2 genes. These mutations impede the body's ability to synthesize essential proteins required for the transport and utilization of cholesterol and various lipids within cellular structures. This metabolic dysfunction results in excessive cholesterol deposition within the liver and spleen, along with an abnormal accumulation of other lipids within neural tissues. This deterioration manifests in impairments related to ocular movements, ambulation, deglutition, auditory processing, and cognitive function.