Title : A case of pityriasis rubra pilaris precipitated by bimekizumab
Abstract:
Pityriasis rubra pilaris (PRP) is a rare chronic inflammatory papulosquamous disorder characterized by orange-red scaly plaques, follicular papules, islands of sparing, and waxy keratoderma. While its etiology remains unclear, triggers such as ultraviolet radiation, tyrosine kinase inhibitors, and vaccinations have been reported. We present, to our knowledge, the first reported case of PRP precipitated by bimekizumab.
A 71-year-old Caucasian man with a history of psoriasis presented with a widespread red scaly rash beginning on the head and extending to the trunk, arms, and legs, causing severe pain and impaired mobility. The eruption occurred approximately six weeks after his first dose of bimekizumab. Examination revealed confluent erythematous scaly plaques with islands of sparing and waxy keratoderma with palmar/plantar fissuring. He was admitted for wet wrap therapy, intravenous antibiotics, and hydration. Punch biopsies demonstrated alternating hyperkeratosis and parakeratosis in a subtle checkerboard pattern, follicular plugging, focal acantholysis, and mild superficial perivascular lymphocytic infiltrate, consistent with PRP. On discharge, he was commenced on acitretin 25 mg twice daily, resulting in significant improvement. At six-month follow-up, he remained well.
This case highlights the potential for bimekizumab to precipitate PRP, expanding the spectrum of drug-induced triggers. Clinicians should be aware of this possibility, particularly in patients receiving biologic therapies. Early recognition and systemic therapy, such as acitretin, can lead to favorable outcomes. Further research is warranted to elucidate the immunopathological mechanisms linking IL-17 inhibition and PRP.
