High prevalence of spondyloarthritis in sarcoidosis patients with chronic back pain

Introduction Chronic back pain (CBP) is a frequent complaint in patients with sarcoidosis, which challenges the clinician as multiples causes may potentially underlie this symptom. Interestingly, some reports suggest that the coexistence of sarcoidosis and spondyloarthritis (SpA) may be frequent. This study aimed to determine the prevalence of axial radiographic and non-radiographic SpA in patients with sarcoidosis and CBP and assess the association between patient characteristics and SpA. Methods This cross-sectional study enrolled 64 patients with a diagnosis of sarcoidosis and CBP. Patients describing CBP underwent a full spine MRI and radiography. All patients with inflammatory CBP underwent complementary sacroiliac joint MRI. The diagnosis of axial SpA was based on the Assessment of SpondyloArthritis International Society classification criteria. Results Among the 64 patients (49 women) with sarcoidosis and CBP, 29 had inflammatory pain; 15/64 had a diagnosis of SpA (23.4% [95% CI: 13.7–35.6], 14/29 (48.3% [95% CI: 29.5–67.5] of those with inflammatory back pain). MRI sacroiliitis was found in 13 patients. On both univariate and multivariate analysis, SpA diagnosis was associated with inflammatory CBP (OR=28.5, 95% CI: 1.91–425.4) and sarcoidosis limited to the thorax (OR=6.74, 95% CI: 1.08–42.1). SpA was associated with young age (p = 0.0093) and male sex (p = 0.021) only on univariate analysis. Besides, 12/64 patients (18.8%, 95% CI: 10.1–30.5) had a diagnosis of sarcoidosis spine bone lesions, 7/64 (10.9%, 95% CI: 4.5–21.2) symptomatic vertebral fracture and 30/64 (46.9%, 95% CI: 34.3–59.8) degenerative spine. Conclusions The prevalence of SpA is increased in sarcoidosis patients with inflammatory back pain. The systematic use of spine and sacroiliac MRI in this subgroup is justified. The association between other patient features and SpA needs further confirmation.