Ultrastructural findings in skin from patients with Niemann-Pick disease, type C.

Niemann-Pick disease, type C is a lysosomal storage disease characterized by hepatosplenomegaly, the presence of foam cells in the reticuloendothelial system, and gradual motor and cognitive decline leading to death. Over 90% of patients demonstrated a defect of cholesterol esterification in cultured fibroblasts. This finding allows a reliable biochemical diagnosis; however, the test is complex and time-consuming and only available in a few centers. Ultrastructural examination of skin biopsy in 5 patients with Niemann-Pick disease, type C demonstrated lysosomes containing loosely arrayed dark lamellated structures within a clear matrix. Affected cells included macrophages, axons, pericytes, Schwann cells, smooth muscle cells, and fibroblasts with relative sparing of vascular endothelium and melanocytes. These findings demonstrate the usefulness of this simple and readily available morphologic test for the diagnosis of Niemann-Pick disease, type C.