Clinical characteristics of peripheral spondyloarthritis without psoriasis, inflammatory enteropathy or preceding infection, from a single rheumatology clinic in northern India

The objective of this study was to characterise the peripheral arthritis of spondyloarthritis (pSpA) excluding psoriatic-, inflammatory enteropathy-related, post-infectious reactive-SpA and arthritis associated with axial SpA/ankylosing spondylitis (axSpA/AS). Patients presenting with the clinical features of the broad spectrum of SpA were screened for the presence of peripheral arthritis using the Assessment of SpondyloArthritis International Society (ASAS) criteria. The other conditions that could cause pSpA, e.g. psoriasis, inflammatory enteropathy, reactive arthritis and axSpA/AS, were excluded. Their assessment included clinical, laboratory and imaging features. Of a total of 405 patients seen within the spectrum of SpA, 25 (6.2%) patients were identified as pSpA with none of the conditions that could be attributed to their disease. The male to female ratio was 2.6:1; the pattern of involvement was predominantly lower extremity asymmetrical large joint oligoarthritis in persons below the age of 40 years (60% were <30 years of age). Some had soft tissue and/or extra-articular manifestations characteristic of SpA (36%) and family history (20%) of SpA spectrum of diseases. When compared to peripheral arthritis reported in axial axSpA/AS, root/central joint involvement was minimal in pSpA. Otherwise, the pattern of arthritis appeared similar. Exclusive peripheral arthritis without the presence of the other disease-defining conditions is uncommon, seen only in 6.2% of the SpA spectrum diseases. The pattern of joint involvement was similar to that observed with axSpA/AS except that the root/central joints were not seen.