Niemann-Pick disease (NPD) is actually a collection of a number of distinct autosomal recessive lysosomal storage diseases. They are divided into two groups of two based on the underlying metabolic deficiency:
- deficiency of acid sphingomyelinase 1,3,4
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Niemann-Pick disease type A (NPD-A)
- severe hepatosplenomegaly in infancy
- severe central nervous system involvement, with atrophy or white matter T2 signal increase on MRI 1
- usually, succumb to the disease by 2 years of age 1,3,4
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Niemann-Pick disease type B (NPD-B)
- hepatosplenomegaly
- minimal CNS involvement 4
- variable age of onset and more indolent clinical course 1
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Niemann-Pick disease type A (NPD-A)
- impaired intracellular cholesterol trafficking 1
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Niemann-Pick disease type C (NPD-C)
- pronounced CNS involvement with atrophy or white matter T2 signal increase on MRI 1
- mild hepatosplenomegaly
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Niemann-Pick disease type D (NPD-D)
- Nova Scotian ancestry 1
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Niemann-Pick disease type C (NPD-C)