Generalized pustular psoriasis in Japan: two distinct groups formed by differences in symptoms and genetic background.

A multi-center study for investigating generalized pustular psoriasis was carried out in Japan in order to clarify the prevalence, the etiology, and the standard therapy. Through questionnaires, 541 cases of patients with generalized pustular psoriasis and related disorders were collected, and the history, the precipitating factors, the symptoms and the laboratory findings were analyzed from medical records. The statistic analysis revealed that 902 (+/- 102.2) patients with generalized pustular psoriasis were expected at the time, and that the prevalence of generalized pustular psoriasis in Japan was 7.46/million. Of 541 patients with generalized pustular psoriasis, 208 cases had the recurrent episodes of symptoms with generalized pustules which had been referred to von Zumbusch type pustular psoriasis or to the acute form of generalized pustular psoriasis. Two hundred and eight patients were further subdivided into two groups: one with a preceding history of ordinary psoriasis (pso+ generalized pustular psoriasis; 65 cases) and another without a psoriasis history (pso- generalized pustular psoriasis; 143 cases). Subdivision into the two groups defined that the onset of pustular outbreak was earlier in the pso- generalized pustular psoriasis group. It was also pointed out that the precipitating factors were different, as the pso- generalized pustular psoriasis group was more frequently affected after infections, and that the pso+ generalized pustular psoriasis group was more frequently affected by preceding corticosterold therapy. HLA analysis of 92 cases with von Zumbusch type generalized pustular psoriasis confirmed that A2, B14, B35 phenotypes were weakly correlated, and when 92 cases were subdivided into the two groups, the pso+ generalized pustular psoriasis group revealed a statistically significant correlation with A1 (p < 0.01), B37 (p < 0.02) and DRw10 (p < 0.05), which was closely related with psoriasis vulgaris patients in Japan. Both clinical surveillance and genetic analysis have disclosed the heterogeneity of von Zumbusch type generalized pustular psoriasis, as there exist two types; one is closely related to psoriasis and the other not.