Serum level of bone morphogenetic protein-7 in relation to entheseal ultrasonography in ankylosing spondylitis patients

To assess serum level of bone morphogenetic protein-7 (BMP-7) and to study its relation to clinical and sonographic assessment of peripheral enthesitis in ankylosing spondylitis (AS) patients. This study involved 49 AS patients and 40 matched controls. The serum BMP-7 level was determined by enzyme linked immunosorbant assay (ELISA). Entheses were assessed by musculoskeletal ultrasound (MSUS) and scored using Madrid Sonographic Enthesitis Index (MASEI). The AS disease activity score-C-reactive protein (ASDAS-CRP), Bath AS disease activity index (BASDAI) and Bath AS Functional Index (BASFI) were assessed. Patients were 45 males and 4 females with a mean age of 35.57 ± 9.71 years and median disease duration of 10 (2–28) years. US lesions were frequently found at the insertions of Achilles (76.5%), quadriceps (57.1%), plantar fascia (51%) and triceps (43.8%) tendons. Serum level of BMP-7 was significantly increased in patients (41.8 ng/ml) compared to controls (38.5 ng/ml) (p = 0.031). BMP-7 serum level significantly correlated with age (p = 0.03), disease duration (p < 0.001) and BASFI (p = 0.02) but did not correlate with ASDAS CRP, BASDAI, clinical enthesitis or total MASEI. Total MASEI correlated significantly with age, disease duration, ASDAS-CRP, BASDAI and BASFI. MASEI is a good predictor of activity in AS patients at a cut-off score of 9. AS patients have a significant higher level of serum BMP-7 compared to control which indicates that it may play an important pathogenetic role in AS. However, this level did not correlate with either clinical or sonographic assessment of peripheral enthesitis.