Pityriasis rubra pilaris (PRP) is a rare and challenging dermatological condition that often mimics other skin disorders, complicating diagnosis and management. This case is unique due to the patient’s comorbidities, which restricted treatment options and required a shift from conventional therapy to biologic treatment.

A 57-year-old male presented with a three-week history of an itchy rash on the face, neck, and upper extremities after sun exposure. Initial treatment with topical corticosteroids was ineffective, and the condition progressed to involve the trunk and lower extremities with erythroderma. Additional findings included hyperkeratosis of the palms and soles, psoriatic plaques on the elbows, and thickened toenails with onychomycosis. Histopathology revealed superficial psoriasiform dermatitis, consistent with PRP. Methotrexate (12.5 mg/week) was initiated, leading to initial improvement. However, a relapse occurred after five months, and due to elevated liver enzymes, a dose increase was not feasible. Secukinumab, an IL-17A inhibitor, was subsequently recommended by the clinic consilium. Already after one month, significant improvement was observed, and near-complete remission was achieved by four months. The patient continues treatment with secukinumab with a satisfactory clinical response and minimal residual symptoms.

This case underscores the complexities of diagnosing and managing PRP, particularly when comorbidities limit standard treatment options. The successful use of secukinumab, despite the failure of conventional therapy, demonstrates the potential of biologics in managing PRP, especially in refractory cases. It highlights the importance of personalized treatment strategies in optimizing outcomes for patients with complex dermatological conditions.