Clinical and radiological characteristics of SAPHO syndrome

The peculiar bone involvement, represented by osteitis, is the common denominator of SAPHO syndrome. Hyperostosis and osteitis are chronic inflammatory reactions involving the cortical and trabecular bone respectively; both are characterised by increased sclerosis. Hyperostosis appears radiologically as chronic endosteal and periosteal thickening with narrowing of the medullary canal, but areas of ostelysis may also be present. Conversely, osteitis appears as increased osteosclerosis involving the trabecular infrastructure of cancellous bone. The occurrence of hyperostosis with little or no osteitis is not uncommon. SAPHO syndrome may have a prolonged course with phases of reacutization and remission; the long-term prognosis is usually fairly good, but sometimes a disabling course may occur. Our experience demonstrated that the majority of patients suffering from SAPHO syndrome experienced a chronic course, requiring continous treatment, whilst in a third of the cases the patients reported multiple remission and exacerbations of the disease with flares lasting till to 8 months. Only in a minority of cases the bone inflammation faded and never recurred. Female sex, peripheral arthritis, ACW involvement, the coexistence of more than one cutaneous symptoms, and high inflammatory indices are correlated with a chronic disease course and involvement of new osteoarticular sites.