Prurigo pigmentosa: clinicopathological study and analysis of 50 cases in Korea

Prurigo pigmentosa is a recurrent dermatosis with severe pruritus and several peculiar clinical features. Its exact etiology and pathogenesis are unclear. The aim of this study was to investigate the clinical features and chronological changes in the histopathology of prurigo pigmentosa in Korean patients and to assess the etiology of this condition. We reviewed the medical records, clinical photographs and biopsy specimens from 50 patients diagnosed with prurigo pigmentosa. Mean age at diagnosis was 23.7 years (range, 15-61 years). Prurigo pigmentosa started as urticarial papules or plaques, changing first to papulovesicles and then to reticulated brownish macules. The most frequent sites were the back and chest, especially depressed areas such as the central back and inter-mammary area. Dietary change was suspected as a cause of prurigo pigmentosa in 17 patients. Histopathologically, early-stage lesions had dermatitis herpetiformis-like features; fully-developed lesions displayed impetigo-like or acute, generalized, exanthematous, pustulosis-like features; and late lesions presented with post-inflammatory hyperpigmentation-like features. Oral minocycline, with or without dapsone, was effective in inhibiting the appearance of new lesions, but did not prevent recurrence. Prurigo pigmentosa is not rare in Korea, is apparently associated with dietary modification and preferentially involves the depressed regions of the trunk.