Abstract
BACKGROUND: Acanthosis nigricans is a skin condition characterized by dark, thickened plaques, typically found in intertriginous regions such as the groin and neck. While commonly associated with obesity and insulin resistance, acanthosis nigricans rarely presents on the scalp. This case report highlights an uncommon presentation of acanthosis nigricans. CASE PRESENTATION: A 16-year-old Iranian male presented with yellowish-brown, scaly papillomatous plaques on the scalp, along with velvety brown plaques in flexural areas. He had a longstanding history of seborrheic dermatitis on the frontal scalp, which had worsened with weight gain and obesity. Otherwise, the patient was healthy. Histopathological examination revealed papillomatosis, hyperkeratosis, and acanthosis. Despite thorough evaluation for systemic diseases, the diagnosis of acanthosis nigricans was confirmed on the basis of lesions observed on other regions of the body. The patient was treated with keratolytic therapy and advised on weight reduction, leading to significant improvement within 2 months. CONCLUSION: While acanthosis nigricans typically manifests in the skin folds, this case highlights the importance of considering acanthosis nigricans as a differential diagnosis in patients with scalp involvement, particularly those with obesity and insulin resistance. Histopathological confirmation remains essential, and management should focus on addressing the underlying etiological factors, as demonstrated by the favorable outcomes achieved through keratolytic therapy and weight management in this patient.