Niemann Pick Disease

Niemann-Pick disease types A and B result from deficient activity of acid sphingomyelinase, encoded by a gene on chromosome 11. The defect results in accumulation of sphingomyelin in the monocyte-macrophage system. The progressive deposition of sphingomyelin in the central nervous system leads to type A, and in nonneuronal tissues leads to type B. Type C is a neuropathic form that results from the defective cholesterol transport.

Clinical Manifestations

Depending on the type, Niemann-Pick disease has classic signs, including:

• Hepatosplenomegaly

• Cherry red spot in macula

• Psychomotor deterioration

• Reticular pulmonary infiltrates

• Foamy cells in the bone marrow

Table 5-8 lists the clinical features of the different types of Niemann-Pick disease. Diagnosis

Diagnosis involves examining leukocytes or cultured fibroblasts to determine sphin-gomyelinase activity.

Table 5-8. Classification of Niemann-Pick Disease

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