Psoriatic onycho-pachydermo periostitis (POPP): a case report treated successfully with IL-17 blockade and a literature review on characteristics, pathogenesis, and treatment.

Psoriatic onycho-pachydermo periostitis (POPP) is characterized by psoriatic onychodystrophy, connective tissue thickening, and periostitis of the distal phalanges (DPs), producing a drumstick-like deformity. Our aim was to present the first case of POPP treated successfully with an IL-17 inhibitor, perform a literature review of its characteristics and treatment, and explore the possible pathogenesis. We conducted a systematic review of previously presented POPP cases. We present a patient with methotrexate (MTX)-resistant treatment POPP, who had significant resolution of symptoms and inflammatory lesions on post-treatment MRI with secukinumab 150 mg. We also identified 31 cases of POPP (27 males; mean age 44.9 years) in the literature review. There was great toe involvement in 24 cases, and distal interphalangeal (DIP) involvement in 14 cases, with frequent radiographically evident damage. Seventeen of 31 patients received systematic treatment other than biologics, mostly MTX, with no satisfactory results. Anti-TNF agents were used successfully in 5 cases, mostly after disease modifying anti-rheumatic drug (DMARD) failure. Imaging studies in nail psoriasis and DIP psoriatic arthritis have shown an anatomical link among the nail, the DP bone, and the DIP joint entheses, suggesting that POPP may be a subtype of nail disease with excessive involvement of DP tissues (nail, soft tissue, enthesis, and bone). IL-17 inhibition could be an alternative therapeutic option in DMARD-resistant cases of POPP. Conventional treatment achieves modest success, but anti-TNF agents appear to be much more effective. Based on imaging studies, POPP may be a particular subtype of nail disease.