Diagnosis of

Niemann-Pick Type C

Niemann-Pick Type C (NPC) is initially diagnosed by taking a small piece of skin ("skin biopsy"), growing the cells ("fibroblasts") in the laboratory, and studying their ability to transport and store cholesterol.

The transport of cholesterol in the cells is studied by measuring conversion of the cholesterol from one form to another ("esterification"). The storage of cholesterol is assessed by staining the cells with a compound ("filipin") that glows under ultraviolet light. It is important that both the transport and storage tests be performed, since reliance on one or the other may lead to an incorrect diagnosis.

Since 1997, over 200 genetic mutations related to NPC have been identified. The number of unique mutations precludes use of genetic testing as a general diagnostic tool. However, genetic testing can be performed to identify carriers in families where the mutation is known. The Mayo Clinic has conducted extensive DNA testing and counseling for patients and families with NPC.

Because NPC is rare and its symptoms quite variable, it is not widely recognized in the medical community. While education efforts by NNPDF have increased awareness of the disease, there are still instances of mis- and delayed-diagnosis.

For additional information about options for genetic testing, contact Cate Walsh Vockley, the National Niemann-Pick Disease Coordinator.

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