Successful treatment of pustulotic arthro-osteitis with bimekizumab: a case report.

Pustulotic arthro-osteitis (PAO) is an inflammatory osteoarticular disorder associated with palmoplantar pustulosis (PPP). Whilst anti-TNF-α agents and IL-23 inhibitors have shown efficacy in PAO, the therapeutic potential of bimekizumab (BKZ), a dual IL-17A and IL-17F inhibitor, remains unestablished. A 53-year-old Japanese man with a history of PPP developed fever and polyarthritis involving the distal interphalangeal joints, shoulders, and knees. Laboratory investigations revealed elevated inflammatory markers, including C-reactive protein and matrix metalloproteinase-3. Imaging studies showed inflammation of the sternum and sacroiliac joints, consistent with PAO. Despite treatment with nonsteroidal anti-inflammatory drugs, methotrexate, adalimumab, and upadacitinib, his symptoms and systemic inflammation persisted. Bacterial cultures were negative, and no other causes of fever were identified. The patient became afebrile the day after switching to BKZ, and both joint and skin symptoms gradually improved thereafter, along with normalisation of laboratory markers. This case highlights the potential utility of BKZ in the treatment of refractory PAO, particularly in cases with systemic inflammation and fever.