All types of Niemann-Pick are autosomal recessive. This means that both parents are carriers -- they each carry one copy of the abnormal gene without having any signs of the disease themselves.

When both parents are carriers, there is a 25% chance that their child will have the disease and a 50% chance that a child will be a carrier.

Carrier detection testing for all families is not yet reliable. The mutations for types A and B have been extensively studied, particularly among the Ashkenazi Jewish population, and DNA tests for these forms of Niemann-Pick are available.

Mutations have been identified in the DNA of many patients with type C Niemann-Pick disease -- carrier detection may be possible. Diagnosis in the fetus is available in a limited number of centers. Carrier detection is possible for other families only after their specific mutation is identified.