Pigmented Prurigo: A Cutaneous Marker of a Metabolic Disorder- A Case Report

Abstract

Background: Prurigo pigmentosa is an uncommon, recurrent inflammatory dermatosis characterised by pruritic papules and subsequent hyperpigmentation. This report describes its presentation in an older woman with obesity and abnormal glucose-related investigations. Case Presentation: A 70-year-old woman from Valencia, Venezuela, presented with a one-year history of intensely pruritic, generalised papular lesions and repeated relapses despite previous treatment. Examination revealed bilateral, symmetrical erythematous-violaceous papules, some forming plaques with excoriations and crusts, predominantly affecting the chest and extremities. Her body mass index was 33.5 kg/m². Skin biopsy demonstrated epidermal hyperplasia, spongiosis, ballooning degeneration, necrotic keratinocytes, parakeratosis, a subcorneal pustule, papillary dermal oedema and a perivascular inflammatory infiltrate, consistent with prurigo pigmentosa. Initial doxycycline, fexofenadine and topical measures did not resolve the lesions. Subsequent testing showed fasting glucose of 125 mg/dl, a two-hour glucose value of 262 mg/dl, fasting insulin of 40.2 uU/ml, postprandial insulin of 181.2 uU/ml and glycated haemoglobin of 7.8%. Dietary adjustment and metformin 500 mg twice daily were followed by substantial clinical improvement after six weeks, with residual hyperpigmentation. Conclusion: The clinical course illustrates the value of evaluating metabolic abnormalities in an older patient with recurrent prurigo pigmentosa. However, ketone measurements were not reported, and the simultaneous interventions do not permit attribution of improvement to a single factor.