Epidemiology of cutaneous tuberculosis in Japan: a retrospective study from 1906 to 2002

Interest in tuberculosis has recently been revived, especially in association with the onset of acquired immunodeficiency syndrome (AIDS). In Japan, the incidence of tuberculosis has declined since the 1950s, but has shown a tendency to increase in the past 10 years.

To determine the patterns of prevalence of cutaneous tuberculosis in Japan, data for cutaneous tuberculosis cases recorded between 1906 and 2002 were obtained from the dermatologic clinic of Kyushu University Hospital. The population of tuberculosis-infected patients was stratified into groups encompassing 10-year periods. Each patient group was then classified as having true tuberculosis or tuberculid, as well as being classified by gender. The total number of patients with cutaneous tuberculosis analyzed was 1324.

The incidence of cutaneous tuberculosis, both true tuberculosis and tuberculid, decreased between 1906 and 1935, increased between 1936 and 1955, and decreased again from 1955. The incidence of true tuberculosis was higher than that of tuberculid between 1906 and 1925. The incidence rates of true tuberculosis and tuberculid were equal from 1926 to 1945, and since 1946 the incidence of tuberculid has been higher than that of true tuberculosis. The incidence of tuberculid decreased between 1986 and 1995, but showed a dramatic increase between 1996 and 2000. The frequency of cutaneous tuberculosis was highest in the 10-49 year age group before 1980, but since 1981 has been highest in groups over 40 years of age.

The incidence of cutaneous tuberculosis in Japan is decreasing and shows a shift towards older generations. However, there is an increase in the incidence of tuberculid, especially in elderly female patients.