A study of individuals with longstanding skin psoriasis but no clinical arthritis or spondylitis has found no evidence of subclinical involvement of the sacroiliac joint or spine.
Courtesy Centers for Disease Control and Prevention
The prevalence of sacroiliac lesions on blinded MRI assessment was similar in 20 patients who had skin psoriasis for a median of 23 years and in 22 healthy controls, and no sacroiliac ankylosis was seen in either group. Similarly, there was no significant difference between the two groups in spinal lesions on MRI, nor in any of the five levels of lesion frequency, Vlad A. Bratu, MD, of the department of radiology at University Hospital Basel (Switzerland) and his coauthors reported in Arthritis Care & Research.
On blinded MRI assessment, five (25%) patients with skin psoriasis and two (9.1%) controls were classified as having inflammation of the sacroiliac joint. Three of these patients in the psoriasis group and one in the control group were older than 50, and the three with psoriasis had had the condition for 26-35 years.
Dr. Bratu and his colleagues said that subclinical peripheral joint inflammation on MRI had previously been a common finding in patients who had skin psoriasis but no clinical signs of psoriatic arthritis. But given the limited evidence of concomitant subclinical axial or spinal inflammation in their study, the authors argued there was no support for routine screening for potential subclinical axial inflammation in patients with longstanding skin psoriasis.
They noted that bone marrow edema lesions in at least two sacroiliac joint quadrants were seen in 35% of patients with psoriasis and 23% of healthy controls, a finding that reflected those seen in other studies in healthy individuals.
“If a specificity threshold for a given MRI lesion of at least 0.9 is applied for axial MRI to discriminate between axial SpA [spondyloarthritis] and background variation in healthy controls or in differential diagnostic conditions, no more than 10% of healthy controls in our study should meet this criterion by an individual level data analysis,” they wrote.
The authors also pointed out the impact of age on lesion frequency, which was more evident in spinal lesions.
“This observation supports the hypothesis that some spinal alterations in higher age may reflect degenerative rather than inflammatory changes,” they wrote. “However, there is a gap in knowledge with virtually no evidence about presence and pattern of degenerative versus inflammatory spinal lesions in subjects beyond 50 years of age.”
The study was supported by the Gottfried and Julia Bangerter-Rhyner Foundation. No conflicts of interest were declared.
SOURCE: Bratu V et al. Arthritis Care Res. 2018 Sep 22. doi: 10.1002/acr.23767.