Prurigo pigmentosa: a clinical and histopathological study of nine Chinese cases.

BACKGROUND: Prurigo pigmentosa (PP) is a chronic and recurrent inflammatory skin disease with the distinctive and prominent feature of reticulate hyperpigmentation. Most known cases have been reported in Japan; here we report nine Chinese cases.

OBJECTIVE: To determine the clinical manifestation of prurigo pigmentosa and its effects in Chinese individuals compared to patients of other ethnicities.

METHODS: We retrospectively analysed nine cases of PP. For all cases, clinical information was collected and reviewed, and skin biopsies were performed. Furthermore, we followed all nine patients to determine the recurrence rate.

RESULTS: All nine patients fulfilled the diagnostic criteria of prurigo pigmentosa. The mean age of the patients at diagnosis was 27.4 years, and the patients were predominantly female. Skin lesions at different stages commonly co-occurred in the same patient. The most commonly affected part of the body was the back, but the armpit was also often involved. Patients responded well to minocycline treatment for the short duration of 8.62 days, and a lower recurrence rate (28.3%) was recorded after treatment. Biopsy revealed classic neutrophil and/or lymphocyte infiltration, spongiosis and necrotic keratocytes. Abscesses occasionally occurred in the follicular orifice. The abnormal presentation of hair follicles was also discovered. All characteristics were found to co-exist in different stages.

CONCLUSION: We conclude that PP is easy to misdiagnose. Histopathological characteristics can co-exist at different stages, consistent with the clinical finding that different stages of skin lesions presented concurrently, contributing to misdiagnosis. Oral administration of minocycline not only yields an excellent response, but also effectively reduces the recurrence rate.