Clinical and histopathological study of generalized pustular psoriasis and subcorneal pustular dermatosis diagnosed at a Tertiary Hospital in Korea

Background: Generalized pustular psoriasis (GPP) and subcorneal pustular dermatosis (SPD) are clinically and histopathologically difficult to distinguish. There have been no comparative studies exarnining these two diseases in Korea. Objective: To investigate the clinical and histopathological characteristics of GPP and SPD. Methods: We evaluated the clinical features, laboratory, and histopathological findings in 16 patients with generalized pustular eruption who had visited our hospital over the past 10 years and reviewed the literature. Results: Ten GPP and six SPD patients were included in the study. The mean age at diagnosis was 44.4 years in the GPP group and 50 years in the SPD group. The number of patients with previous personal history of psoriasis vulgaris was 2 (20%) for GPP and 0 (0%) for SPD. The number of patients with history of recent exposure to medications was 1 (10%) and 0 (0%) in the GPP and SPD groups, respectively. Symptoms of fever, arthralgia, and mucosal involvement were reported in 10%, 20%, and 10% of GPP patients and 16.7%, 16.7%, and 0% of SPD patients, respectively. Leukocytosis, eosinophilia, elevated ESR/CRP, and elevated AST/ALT were reported in 25%, 0%, 25%, and 50% of GPP patients and in 20%, 0%, 40%, and 40% of SPD patients, respectively. On histological findings, in the GPP group, spongiosis, and psoriasiform changes including hyperkeratosis/parakeratosis, and rete ridge changes were more apparent than in the SPD group. The mean period of clinical improvement was 32.9 days with 40% recurrence in the GPP group and 38.3 days with 66.7% recurrence in the SPD group. Conclusion: Although GPP and SPD exhibit clinical and laboratory findings that are similar and difficult to differentiate, systematic analyses including clinical course, laboratory findings, and histopathological findings are helpful for an accurate differential diagnosis.