A Case of Neutrophilic Dermatoses-Sweet's Syndrome Coexisting with SAPHO Syndrome.

SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis) syndrome is a rare disease characterized by osteoarticular and cutaneous manifestations. SAPHO syndrome mostly involves the skin, mainly presented as palmoplantar pustulosis and severe acne. Sweet's syndrome (SS) is a neutrophilic dermatosis of unknown cause, which may be caused by autoinflammation. So far, SAPHO syndrome complicated with SS has been rarely reported worldwide. Here, we present a rare case diagnosed in our hospital with detailed clinical information. This patient presented pain and swelling in her right leg. Later, she developed red papules on her right lower eyelid and a skin biopsy showed diffuse lymphocytic and neutrophilic infiltration in the superficial dermis. She was diagnosed with SAPHO syndrome and SS according to medical history and examination. These two diseases share parts of autoinflammatory signaling pathways and might be different variations of the spectrum of autoinflammatory diseases. Through this case, we aim to provide a new horizon for the regulation of neutrophils in SAPHO syndrome and skin lesions like SS.