Distribution of age at onset and its influence on clinical characteristics of 164 patients with synovitis, acne, pustulosis, hyperostosis, and osteitis syndrome

Abstract

Objective To investigate the distribution of age at onset and its influence on clinical char-acteristics in synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome. Methods We recruited 164 patients with SAPHO syndrome who presented to Peking Union Medical College Hospital from Jan 2004 to Mar 2015. All the patients were assessed for medical history, laboratory tests and imaging presentations. The distribution of age at onset was analyzed using Shapiro-Wilknormality test and Kolmogorov-Smirnov test for mixed normal distribution. The influence of age at onset on clinical features was analyzed using Mann-Whitney U test and χ2 test. Results A double-peak mixed normal distribution of age at onset of skin lesions was found in female patients with SAPHO syndrome, with means and standard deviations of (30±6) years (early-onset) and (51±7) years (late-onset) for each mixed normal distribution. The cut-off point was determined to be 42 years old. Nonetheless, a typical single-peak normal distribution of age at onset of skin lesions was observed in male patients. A significantly higher frequency of thoracic region pain [14/36(38.9%) vs 6/70(8.6%),χ2=14.28, P<0.01, spinal lesions revealed by bone scintigraphy [23/35(65.7%) vs 23/66(34.8%), χ2=8.79, P=0.003], and peripheral skeletal lesions revealed by bone scintigraphy [17/35(48.6%) vs 17/66(25.8%),χ2=5.33, P=0.021] were found in late-onset female patients compared with early-onset ones. Moreover, female patients with late onset had significantly higher hs-CRP level [(12±12) mg/L vs (9±11) mg/L; U=911.5, P=0.042)], pain VAS (4.8±1.8 vs 4.0±2.1; U=948, P=0.036), and BASFI (3.0±2.2 vs 1.8±2.0; U=822.5, P=0.003) at baseline than those with early onset. Conclusion Female patients with SAPHO syndrome have a double-peak distribution of age at onset of skin lesions. Female patients with early and late onset of skin lesions exhibit distinct clinical characteristics. Key words: Acquired hyperostosis syndrome; Age of onset; Psoriasis