Clinical and biochemical diagnostics of Niemann-Pick disease.

Niemann-Pick disease (NPD) is an inherited lysosomal storage disorder characterised biochemically by a deficiency of sphingomyelinase activity and massive accumulation of undegraded sphingomyelin. There are three main clinical types of the disorder (NPD type A, B and C). NPD type A and B is diagnosed biochemically on the basis of measuring sphingomyelinase activity in leukocytes or cultured fibroblasts. The diagnosis may be established with the chromatographic method by the high level of sphingomyelin concentration in liver samples. Because in NPD type C the decrease of sphingomyelinase activity is moderate and only occurs in fibroblasts the thin-layer chromatography of the total liver lipid extracts is necessary for establishing the diagnosis. The thin-layer chromatography of the total liver lipids is sufficient for the diagnosis of all types of NPD.