When skin speaks: Unmasking xanthoma disseminatum in a case of AVP deficiency

ABSTRACT A 35-year-old male presented with progressive polyuria and polydipsia over 6 months, accompanied by non-pruritic, hyperpigmented papulo-nodular skin lesions predominantly in flexural areas. Water deprivation test and response to vasopressin confirmed arginine vasopressin deficiency (AVP-D). Magnetic resonance imaging (MRI) revealed a thickened pituitary stalk with enhancement, suggesting infundibulo-neurohypophysitis. Skin biopsy identified foamy histiocytes with CD68 and CD163 positivity, consistent with a diagnosis of xanthoma disseminatum (XD). Treatment with desmopressin effectively managed polyuria, while cyclophosphamide and atorvastatin partially resolved skin lesions. This case underscores the importance of considering systemic causes of AVP-D, such as XD, when dermatological findings are present.