Two cases of elderly-onset hereditary neuropathy with liability to pressure palsy manifesting bilateral peroneal nerve palsies.

Hereditary neuropathy with liability to pressure palsy (HNPP) is characterized by recurrent focal neuropathies, which usually become symptomatic in the second or third decade of life. However, clinical phenotypic heterogeneity among patients with HNPP has recently been reported. Certain patients show polyneuropathy-type diffuse nerve injuries, whereas others remain asymptomatic at older ages. We present two cases of elderly-onset bilateral peroneal nerve palsies with diffuse muscle weakness in the lower limbs and glove-and-stocking type sensory disturbance. Both patients were diagnosed with HNPP by genetic analyses that detected deletions of chromosome 17p11.2 in peripheral myelin protein 22 genes. Their clinical courses suggested that the Japanese sitting style termed 'seiza', a way of sitting on the floor with the lower legs crossed under the thighs, was a precipitating factor for the bilateral peroneal nerve palsies.