Epidemiological Immunological Studies on Leprosy in Okinawa: I. A Survey on Personal and Family Histories of Inpatients

Personal and family histories of the totally 864 patients with leprosy admitted in the National Leprosaria Okinawa Airakuen and Miyako Nansei-en were surveyed since 1973, for the purpose of understanding epidemiological and immunological characteristics of leprosy in Okinawa. Frequency of intermarriage in the parents of index cases was not significantly higher than that in the public near Miyako Nansei-en. The intermarriage did not correlate with the classification of leprosy in the index cases nor with the incidence of leprosy in other members of their family. It is therefore unlikely that leprosy is associated by recessive gene. Consanguineous patients with leprosy were more frequently found in the index cases with younger age than those in the elder and in the cases with lepromatous leprosy than those with tuberculoid. The frequency in 778 siblings of index cases was 19.9%, indicating a significant difference with that (8.9 %) in 563 parents and children, and these percentages were significantly higher than the incidence rate of leprosy (2.1%) in 191 spouses of index cases. A coincidence in the classification of leprosy was found in 37 out of 53 (69.8%) pairs of consanguineous inpatients, but the percentage was not significantly different among three groups of consanguinity, i. e. parent and child, siblings and the others. These facts seem to indicate that the susceptibility to leprosy is not so largely associated by genetic factors as expected previously. On the other hand, a long period of household contact with index cases did not necessarily increase the frequency of affected cases in the family. The percentage of lepromatous leprosy in the index cases was highest in those who had household contact of 10-15 years and their age at onset was significantly younger than those without household contact. The percentage was also significantly different according to the place at onset. These acts seem to indicate that the susceptibility to leprosy is greatly influenced by postnatal factors such as the household contact at childhood, physiological, immunological and living conditions.