Unusual case of prurigo pigmentosa on the upper extremities in an adolescent female: A rare presentation.

A 16-year-old girl developed prurigo pigmentosa (PP) following initiation of a ketogenic diet, presenting with pruritic, erythematous, and brownish papules exclusively on her upper extremities. Histopathological examination revealed mild spongiosis with perivascular neutrophilic and mononuclear cell infiltrate, confirming the diagnosis of PP. Treatment with oral doxycycline and discontinuation of the ketogenic diet led to lesion resolution within one month, with subsequent postinflammatory hyperpigmentation. This case highlights the rarity of PP presenting solely on the upper extremities in pediatric patients, expanding our understanding of this dermatological disease.