Prurigo Pigmentosa and Confluent and Reticulated Papillomatosis a Spectrum of One Disease: A New Case Report

Abstract

Background: Prurigo Pigmentosa (PP) is a rare inflammatory dermatitis first discovered in 1971. Characterized by a sudden eruption of pruritic reticulated, pink-brown papules coalescing into plaques distributed symmetrically over shoulders, neck, chest, and back. Various triggers have been identified, including the ketogenic diet. Clinicopathological presentation looks similar to confluent and reticulated papillomatosis (CARP) which is a rare dermatosis of unknown etiology characterized by hyperkeratotic pigmented papules & peripheral reticulation involving seborrheic areas. Aim: To document a new case presentation of PP caused by a low-carbohydrate restricted diet and discuss the comparison with CARP clinically, pathologically, and treatment modalities. Case report: A 15-year-old childhood male developed PP 3 weeks after self-initiating a low carbohydrate-restricted ketogenic diet for weight management. Clinically and histopathologically the lesion looks similar to CARP, treated successfully with re-introduction of high carbohydrates in his food, a short course of systemic steroids in combination with oral doxycycline capsules for the one-month duration. Conclusion: PP & CARP have been considered a spectrum of one disease, and PP is a pruritic variant from CARP caused by a low carbohydrate-restricted diet.