Pityriasis Rubra Pilaris and underlying malignancy.

A 59-year-old man presented with a five-month history of widespread, salmon-colored, scaly plaques. Skin examination revealed salmon-colored plaques with "islands of sparing" on the trunk and waxy keratoderma on the palms and soles. Histopathology of the lesion showed alternating orthokeratosis and parakeratosis in vertical and horizontal directions, consistent with a diagnosis of pityriasis rubra pilaris (PRP). The patient was unresponsive to methotrexate and Secukinumab. Further evaluation through a computerized tomography scan revealed a presence of air-filled multicystic changes in the upper left lung, accompanied by diffuse pulmonary bullae. Elevated serum tumor markers, including CEA, NSE, and SCC, indicated an underlying acinar-predominant adenocarcinoma, suggesting a paraneoplastic PRP. He was subsequently referred to the oncology department for further management. This report underscores the importance of identifying an underlying malignancy in recalcitrant PRP cases.