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Training Level

Resident PGY 3


Henry Ford Hospital


Introduction: Prurigo pigmentosa is a rare inflammatory dermatosis characterized by pruritic erythematous papules and papulovesicles on the back, neck and chest. The cause is not well elucidated, but it has been associated with ketotic states. We present the second case of prurigo pigmentosa after gastric bypass surgery. Case: A 38 year-old African American female presented for evaluation of a rash on her neck, chest and back that initially began 2 weeks after gastric bypass surgery. It began with pruritus of the palms and small pruritic papules on her lower back. It spread to involve patchy areas of the lower back, chest, lateral neck and behind the ears. New lesions continued to appear every few days and old lesions would resolve with hyperpigmentation. On exam, indurated papules were noted in clusters behind both ears, on her right lateral neck, beneath the breasts, and in a linear band on the midline lower back. A punch biopsy showed superficial and deep lymphocytic inflammation and focal interface dermatitis. Endothelial cells were swollen, there was red cell extravasation and rare eosinophils were noted. She was started on minocycline 100 mg twice daily for two weeks. The eruption resolved and remained quiescent even after discontinuing minocycline, although she had residual hyperpigmentation. Conclusion: Prurigo pigmentosa is a rare inflammatory dermatosis that starts as crops of inflammatory lesions that undergo multiple stages. Lesions involute within a week and leave macular reticulated hyperpigmentation. It occurs more commonly in young adults, especially females. Traditionally, it had been described in the Japanese population, however recently there have been cases reported in the Middle East and Western Countries. The exact cause and pathogenesis is still unclear. However, it has been associated with ketotic states seen in dieting, diabetes mellitus, soft-drink ketosis and religious fasting. Studies have found elevated blood and urine ketones in patients with prurigo pigmentosa and noted clearance of skin lesions when ketosis resolved. There has been one prior report of prurigo pigmentosa following bariatric surgery, and we present the second. The histological features vary depending on the stage of the condition. Prurigo pigmentosa is believed to be mediated by neutrophils and patients respond well to medications that have an anti-neutrophil effect including tetracyclines and dapsone. Recurrence may occur after treatment cessation.

Presentation Date


A Pruritic Eruption Following Gastric Bypass Surgery