Approximately 20% of adults with axial psoriatic arthritis (PsA) show active or structural spinal changes without changes in the sacroiliac joint, based on imaging data from 106 individuals.
Axial PsA has been historically grouped with axial spondyloarthritis (axSpA), but it has received more attention in recent years as a condition potentially distinct from axSpA, Henriette Käding, an MD and PhD student in the department of gastroenterology, infectiology, and rheumatology at Charité-Universitätsmedizin Berlin, said in her research presentation at the annual meeting of the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA). She added that the debate persists as to whether these conditions are on the same spectrum or should be separated.
Data from previous studies suggest differences in genetic, clinical, radiographic, and prognostic characteristics between axial PsA and axSpA that may affect patients’ response to available treatments. However, there are relatively little data available on distinguishing imaging and clinical features, and there’s a lack of classification criteria for axial PsA, Ms. Käding said.
Ms. Käding and colleagues prospectively collected data from 106 patients with axial PsA between August 2019 and June 2023 and presented the baseline data of this longitudinal project at the GRAPPA annual meeting in Dublin. At baseline, the researchers conducted clinical assessments of the participants, along with blood sampling, stool samples, and imaging protocols that included MRI of the whole spine and sacroiliac joint (SIJ).
The mean age of the included patients was 44.5 years; 55.7% were female. Inflammatory back pain was present in most of the patients at baseline (78.4%), and 48.1% were positive for HLA-B27, a genetic risk factor for both axSpA and axial PsA. Approximately one-third of the patients had elevated C-reactive protein (> 5 mg/L). In the baseline MRI scans, active inflammatory changes in the sacroiliac joints (SIJ) were seen in 51.9% of the patients and structural changes in 72.1%. MRI spine scans showed active changes in 58.7% of the patients. Notably, active and/or structural changes of the spine without changes in the SIJ appeared in 20% of the patients, Ms. Käding said.
With regard to existing classification criteria, the researchers observed that 92% of the patients met the CASPAR (Classification Criteria for Psoriatic Arthritis) criteria for PsA, 73% met the ASAS (Assessment of Spondyloarthritis International Society) criteria, while 66% of patients met both ASAS and CASPAR criteria.
The study will be the first to include longitudinal MRI scans of the whole spine and SIJ in addition to conventional radiographs, Ms. Käding said.
Better characterization should improve treatment
“Axial involvement in PsA might, on one hand, go unnoticed, but on the other hand, it could also be misdiagnosed in patients with degenerative spinal disease,” Denis Poddubnyy, MD, one of the study coauthors, also of Charité-Universitätsmedizin Berlin, said in an interview.
“By comprehending the unique characteristics, progression, and treatment responses within the axial domain, rheumatologists can customize interventions and therapies to effectively manage the psoriatic disease,” Dr. Poddubnyy said.
“One of the most significant findings [of the current study] is the relatively high frequency of spinal involvement without sacroiliac joint” involvement, Fabian Proft, MD, of Charité-Universitätsmedizin Berlin and senior author of the study, said in an interview. “This finding holds importance as, in primary axial SpA, the disease typically originates in the sacroiliac joints. In contrast, in PsA, the scenario differs, which has implications for the diagnostic approach in clinical practice.”
“In individuals with PsA, spinal involvement can occur independently of sacroiliac joint [involvement]. As a result, imaging studies conducted on patients suspected of having axial PsA should encompass not only the sacroiliac joints but also the spine,” Dr. Poddubnyy explained. “It is important to note, however, that imaging findings such as bony spurs and bone marrow edema might be caused by degeneration or mechanical issues and, therefore, need to be interpreted with caution within the clinical context.”
The study was supported in part by an unrestricted research grant from Novartis. Dr. Poddubnyy and Dr. Proft disclosed receiving research grants and consultancy payments from Novartis and serving on speaker bureaus for the company.