Coincidence of pachydermoperiostosis and synovitis, acne, pustulosis, hyperostosis, osteitis syndrome, a causal or casual association?

Pachydermoperiostosis (PDP) is a rare disorder characterized by skin thickening, acropachia, and periostosis. Synovitis, acne, pustulosis, hyperostosis, osteitis (SAPHO) syndrome is also an orphan disease featured by different dermatological and osteoarthritic manifestations. Herein, we report the first case of an adolescent male diagnosed with both PDP and SAPHO syndrome, presenting with digital clubbing, polyarthralgia, ostealgia, pachydermia and acne on his face, chest and back. Furthermore, we distinguish the characteristics of both diseases and explore the potential pathological mechanism for this coexistence in one patient. Further investigations are needed to establish the detailed pathophysiological association of these 2 diseases.