Objectives: Sarcoidosis is a chronic granulomatous multisystem disease in which arthritis is relatively common. Arthritis of the sacroiliac joints (sacroiliitis) has been described in sarcoidosis but is thought to be rare. The objective of this study was to determine the prevalence of sacroiliitis in a secondary-care population of patients with sarcoidosis.
Methods: Patients attending a specialist secondary-care sarcoidosis clinic underwent evaluation of spinal symptoms using a standard back pain questionnaire, examination of spinal mobility, and laboratory measurements of erythrocyte sedimentation rate, C-reactive protein, serum angiotensin-converting enzyme, and neopterin/creatinine ratio. Tissue typing for the presence of the human leukocyte antigen (HLA)-B27 allele was undertaken. Radiographs of the sacroiliac joints were obtained in each patient and reviewed independently by two observers; a further observer reviewed disputed radiographs.
Results: Sixty-one patients completed the assessments (80.3% of all patients invited to participate). Forty-nine of 61 patients (80.3%) reported having back pain at some point in their lives. Thirty-one of 61 patients (50.8%) had a score on the back pain questionnaire suggestive of inflammatory spinal disease, but only 3 of these patients had erosive damage of the sacroiliac joints on radiography indicating sacroiliitis. One further patient had erosive damage on radiography, making a total of four individuals with evidence of sacroiliitis, a prevalence of 6.6%. Four patients (one patient with sacroiliitis) were positive for HLA-B27. The back pain questionnaire had a sensitivity of 75% and a specificity of 51% for sacroiliitis in this population.
Conclusion: The prevalence of spondyloarthropathy in the normal population has been estimated to be 1.9%. In the sarcoid population studied the prevalence was 6.6% suggesting a possible association between these two conditions. The standard back pain questionnaire for the identification of inflammatory spinal disease had a low sensitivity and specificity in this population.