Nature versus nurture in the spectrum of rheumatic diseases: Classification of spondyloarthritis as autoimmune or autoinflammatory

Familial Mediterranean fever is associated with a wide spectrum of inflammatory disorders: results from a large cohort study

Familial Mediterranean fever (FMF) is characterized by recurrent short-lived/self-limiting inflammatory attacks. Besides these, a substantial number of patients with FMF present with a variety of other inflammatory diseases; however, this issue has not been systematically studied previously. Hence, we aimed to investigate the frequency of inflammatory comorbid diseases in a large FMF cohort. All patients were recruited from "FMF in Central Anatolia (FiCA) Cohort", comprising 971 (mean age 35.3 ± 12 years, 61.5% female) adult subjects. All patients fulfilled Tel Hashomer criteria. Demographic data, FMF disease characteristics, MEFV gene mutations, and comorbid inflammatory diseases were meticulously questioned, and laboratory features and genotype data were retrieved from hospital records. There were comorbid inflammatory diseases in 205 (21.1%) patients. The most common inflammatory disease was spondyloarthritis (12.9%). Other remarkable inflammatory disorders were psoriasis, immunoglobulin A vasculitis/Henoch-Schönlein purpura, Behçet's disease and inflammatory bowel diseases. Cryptogenic organizing pneumonia is a newly defined entity in our cohort which is seemed to be associated with FMF (0.3%). Number of patients with persistent inflammation was higher in those with comorbid diseases (p < 0.001). Our results suggest that FMF is commonly associated with other inflammatory diseases. Therefore, clinicians should be cautious about comorbid inflammatory diseases in FMF patients, particularly in those with persistent inflammation. Identification of pathogenic pathways linking FMF to these diseases warrants further investigations.

TRAF6 neddylation drives inflammatory arthritis by increasing NF-κB activation

Neddylation is a process similar to ubiquitination, and is critical in various inflammatory diseases; however, its importance in the pathogenesis of inflammatory arthritis is not well understood. Here, we investigated the role of neddylation in collagen-induced arthritis (CIA) and its clinical relevance. We showed that neddylation-related genes, including NEDD8 and CULLIN-1, were significantly upregulated in inflamed arthritic synovia. Functionally, neddylation activation was crucial for synovitis of CIA, as the inhibition of neddylation by MLN4924 significantly suppressed synovial cell proliferation and inflammatory responses. Mechanistically, neddylation mediated inflammatory arthritis by regulating NF-κB activation in fibroblast-like synovial cells (FLSs). Furthermore, TNF receptor-associated factor 6 (TRAF6) neddylation at Lys124 was essential for IL-17A-induced NF-κB activation. Replacing the Lys-124 residue with Arg (K124R) resulted in significantly impaired conjugation of NEDD8 to TRAF6, as well as markedly attenuated IL-17A-induced NF-κB activity. Therefore, the pathogenic role of neddylation in CIA as well as its mechanism of action demonstrated here provides a new insight into understanding the role of post-transcriptional modifications in the arthritis inflammatory response.

All that glitters is not gold: sacroiliitis

Objectives

The aim of this study was to determine the prevalence of „rheumatic” and „non-rheumatic” changes of the sacro-iliac joints (SIJ).

Material and methods

We performed MRI in 210 patients with suspected inflammatory low back pain. We sorted and analysed the characteristics of sacroiliac bone lesions in „rheumatic” and „non-rheumatic” patients and assessed the diagnostic values of their extent and location. SIJ lesions were classified on the basis of their location into two categories: unilateral and bilateral. Their extent was then measured and assigned to one of two groups: <1 cm or ≥ 1 cm.

Results

In 45 cases (21%), the MRI findings matched the clinical diagnosis of „rheumatic” sacroiliitis. Interestingly, in 99 cases (47%) the SIJ changes were classified as „non-rheumatic”. L5–S1 degenerative changes, scoliosis and pelvic asymmetry were most frequently encountered as concomitant phenomena in our study.

Conclusions

MRI of the sacroiliac joints in patients suspected of inflammatory low back pain demonstrated more often “non-rheumatic” changes.