Paediatric SAPHO syndrome with pleural effusion: Case report of a unique finding in a rare disease

Synovitis, acne, pustulosis, hyperostosis, osteitis (SAPHO) syndrome is a rare autoinflammatory disease characterised by bone inflammation and skin manifestations including acne, palmoplantar pustulosis, psoriasis, or hidradenitis suppurativa. SAPHO syndrome is considered on the same spectrum as chronic nonbacterial osteomyelitis/chronic recurrent multifocal osteomyelitis, the former often being the nomenclature in adults and the latter in children. The diagnosis is made on patterns of clinical manifestations and is a diagnosis of exclusion. While skin and bone manifestations are commonly described with SAPHO syndrome, pleural involvement is rare, and few cases have been described in the literature, especially in paediatric patients. Herein we present a 14-year-old female with a past medical history of hidradenitis supprtiva, eczema, psoriasis, and a prior episode of culture-negative osteomyelitis who presented to the emergency room with chief complaints of right-sided pain with inspiration and back pain. Exam revealed palmoplantar pustulosis, hidradenitis supprativa, psoriasis, and tenderness of vertebrae. Imaging showed a right-sided pleural effusion and multiple sites of osteitis. Laboratory evaluation revealed elevated inflammatory markers, an exudative pleural effusion with neutrophilic predominance, and no evidence of malignancy, infection, or immunodeficiency. The patient was diagnosed with SAPHO syndrome and treated with naproxen, methotrexate, and golimumab with significant improvement including resolution of the pleural effusion. Paediatric SAPHO syndrome is a rare disease that classically causes osteitis and skin manifestations. This case highlights that pleural effusion can be a rare manifestation of paediatric SAPHO syndrome. Patients with suspected SAPHO syndrome with respiratory symptoms should be evaluated for pleural effusion.