[A family with hereditary neuropathy with liability to pressure palsies--clinical, electrophysiological, pathological study and DNA analysis].

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant disease that causes episodes of recurrent mononeuropathies following minor trauma or pressure. It was recently reported that deletion of the peripheral myelin protein-22 (PMP-22) gene was associated with HNPP in three unrelated American pedigrees and one Dutch pedigree, but not in another Dutch pedigree. We tested a Japanese family with HNPP for PMP-22 gene deletion. HNPP diagnosis was established by a history of recurrent mononeuropathies following moderate compression, delayed distal latencies and F-wave latencies, and the characteristic focal thickening of the myelin sheath ("tomacula") in sural nerves. Genomic DNA of the HNPP patients was extracted from peripheral blood lymphocytes. The DNA was cut by the restriction endonuclease BamHI, separated by electrophoresis and the fragments hybridized with probes for PMP-22 cDNA and human muscle specific phosphoglycerate mutase (PGAM) cDNA (used as internal control). The intensity of the autoradiographs of patients was measured densitometrically and compared to that of normal controls. Our analysis revealed that the PMP-22 and PGAM autoradiograph intensity ratio in the specimens of the HNPP patients was 60% of that of control individuals, thus suggesting that the patients only had a single copy of the PMP-22 gene. From these data we conclude that the PMP-22 gene also was deleted in the Japanese family with HNPP.