Dysregulation of P2X7 receptor-inflammasome axis in SAPHO syndrome: successful treatment with anakinra

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Sir, The syndrome of Synovitis Acne Pustulosis Hyperostosis Osteitis (SAPHO) is a rare condition characterized by a variable combination of osteoarticular and cutaneous manifestations [1]. Although often related to the SpAs, emerging evidence suggests that SAPHO might be a primitive inflammatory osteitis, probably related to polygenic auto-inflammatory disorders [2]. In this report, we describe a dysregulation of extracellular ATP-dependent P2X7-IL1β axis in a case of SAPHO syndrome effectively treated with the IL-1 receptor antagonist (IL-1Ra) anakinra. A 47-year-old female, was admitted to our unit in July 2007 with a 3-year history of remitting pain and swelling of anterior chest wall (ACW) structures, and a 10-year history of severe palmoplantar pustulosis (PPP). During adolescence she suffered from acne conglobata. Total white blood cell (WBC) count was 14.5 × 109/l; ESR was 35 mm/h (normal range <20) and CRP was 1.8 mg/dl (normal range <0.6). HLA-B27 antigen was negative. A CT scan of ACW revealed massive osteitis with periostitic and erosive aspects. A diagnosis of SAPHO syndrome was made, and therapy with SSZ (3 g/day) was set up for 6 months without any significant improvement. The patient was further evaluated in February 2008, after appearance of intermittent right knee arthritis. A slight leucocytosis and elevated acute-phase markers were still present (ESR and CRP were 28 mm/h and 1.1 mg/dl, respectively). At that time, the patient also referred low-grade fever and asthenia. Joint SF showed 7800 cells (65% of monocytes). SF cultures for Propionibacterium acnes resulted negative and so did the PCR for 16S ribosomal RNA and lipase genes. Technetium 99m (99mTc) bone scan revealed hypercaptation at the manubriosternalis syncondrosis and at the right sternoclavicular joint. As increasing evidence suggests that IL-1β might be involved in chronic inflammatory diseases of unknown origin, at the time of this second hospital admission we investigated whether a dysfunction in the processing and release of this cytokine was present [3].

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