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INTRODUCTION Prurigo pigmentosa is a rare inflammatory dermatosis characterized by pruritic and reticulate papules on the trunk leaving hyperpigmentation. This dermatosis has been rarely described outside Asia. The pathophysiology remains obscure. CASE REPORT We report the case of a 21-year-old North-African woman presenting with a highly pruritic eruption with numerous erythematous macules and papules coalescing in a reticular pattern on the trunk. The eruption occurred during the first trimester of pregnancy, which was marked by severe vomiting resulting in weight loss of 13kg with ketonemia and ketonuria. Taking into account the characteristic pattern of the eruption, the absence of differential diagnosis, and the histological examination, we concluded on a diagnosis of prurigo pigmentosa. Progression of the disease exhibited phases of decreased inflammation and of pruritus alternating with episodes of inflammatory flares triggered by relapses of ketonemia. The symptoms finally resolved during the 2nd trimester of pregnancy after vomiting ceased. Secondary reticulated hyperpigmentation was observed. CONCLUSION Although rare, the highly evocative clinical presentation of the eruption should help clinicians in diagnosing prurigo pigmentosa. While pathophysiology remains undetermined, prurigo pigmentosa was reported in cases of intense fasting, anorexia, type-1 diabetes, and in two other cases of pregnancy with severe vomiting. Our case underlines the need to screen for and treat underlying ketonemia to achieve control of the inflammatory flares of prurigo pigmentosa.