Uncompacted myelin in hereditary neuropathy with liability to pressure palsies with the 17 p11.2 deletion.

A 16-year-old girl with a typical features of hereditary neuropathy with liability to pressure palsies (HNPP) and deletion on chromosome 17p11.2 was described. In the mother who was asymptomatic the same genetic defect was found. In a sural nerve biopsy obtained from the girl myelin thickenings characteristic for this disease and de- and remyelination in nerve fibers were found. Special attention was paid to the occurrence of uncompacted myelin, which was present in diffuse and focal forms. It is concluded that high amount of uncompacted myelin is characteristic for HNPP and it is probably related to the under-expression of peripheral myelin protein 22.