Prurigo pigmentosa: a clinicopathologic study of 4 cases from the middle East.

Prurigo pigmentosa (PP) is a rare inflammatory dermatosis originally reported in Japan. Since then, most reports have originated from Asia, and to a lesser extent from Europe. Although the pathogenesis remains unclear, it is now established that PP is linked to ketoacidotic states. Four patients diagnosed with PP were identified from the dermatopathology database at the American University of Beirut Medical Center between January 2009 and December 2013. Clinicopathologic findings in the 4 patients were similar to those previously reported in the literature. The patients were all female with a mean age of 23.5 years. They all presented with itchy erythematous reticulated papulovesicles/plaques leaving variable reticulated brownish patches. Two patients had, in addition, annular lesions arranged en cocarde and pustules, respectively. In 3 patients, the rash was associated with fasting or dieting. The rash had a predilection to the trunk and proximal part of the upper extremities. One patient had intergluteal area involvement. Two biopsy specimens revealed psoriasiform hyperplasia and neutrophilic exocytosis mimicking psoriasis or an impetiginized spongiotic dermatitis. One biopsy specimen exhibited a mild superficial perivascular lymphocytic infiltrate with ballooning and reticular degeneration, a picture mimicking a viral exanthema. Another biopsy specimen exhibited a picture similar to chronic spongiotic dermatitis. Although mostly described in Japan, PP has been described much less frequently in the Middle East region likely due to mis/underdiagnosis. Therefore, increased awareness is necessary especially because fasting is a common religious practice among Arab countries. Further investigations are necessary to better understand the etiopathogenesis of this rare entity.