Epidemiology of hereditary sensory and autonomic neuropathy type IV and V in Japan.

Hereditary sensory and autonomic neuropathy (HASN) refers to a group of rare congenital disorders characterized by loss of pain sensation and other sensory or autonomic abnormalities. Among them, a relatively large proportion of patients with HSAN type IV, which is accompanied by anhidrosis and intellectual disability, are reported from Israel and Japan. HSAN type V, with normal sweating and mental development, is rarely reported in Japan. In 2009, we founded a research group for congenital insensitivity to pain and performed the first epidemiological survey of HSAN types IV and V in Japan. Questionnaires were sent to a total of 3,488 certified training institutions of five nationwide medical societies comprising pediatricians, neurologists, orthopedic surgeons, and dentists. Answers were obtained from 1,610 institutions, and 192 HSAN patients (152 with type IV and 28 with type V) were reported from 105 institutions. After excluding duplicated patients, we identified a total of 62 current, 36 past, and five deceased patients for HSAN-IV, and a total of 14 current, 13 past, and 0 deceased patients for HSAN-V. Using these figures, we estimated that the number of Japanese patients with HSAN types IV and V as 130-210 and 30-60 patients, respectively. We identified no gender differences, and patients with a family history of the disorder were limited to affected siblings in both conditions. Most patients with HSAN-IV were 5-40 years of age, whereas half of the patients with HSAN-V were 40 years or older.