The immune pathology of bursitis in rheumatic inflammatory diseases, degenerative conditions and mechanical stress: A systematic review.

OBJECTIVE

To summarize current insights on the immune pathology of bursitis caused by rheumatic inflammatory diseases, degenerative conditions, or mechanical stress and identify knowledge gaps in this field. Data on tenosynovitis pathology was included for comparison.

METHODS

We performed a systematic review encompassing an electronic database search of all published literatures in PubMed/MEDLINE from inception to February 13, 2023, investigating the immunological changes occurring in the bursa of patients with inflammatory rheumatic diseases, degenerative conditions or mechanical stress (e.g., impingement syndrome).

RESULTS

Thirty-two articles provided data on the immune pathology of bursal tissue inflammation were identified. Histological and immunological perturbations included alterations of tissue morphology, infiltration of macrophages and some T cells, and enhanced expression of proinflammatory cytokines, such as interleukin (IL)-6, IL-1β and tumor necrosis factor alpha (TNF-α). These changes were described for all three underlying causes, although studies on bursitis associated with rheumatic inflammatory diseases were rare. Fibrosis was only reported in subacromial bursitis caused by mechanical stress within our included studies.

CONCLUSION

Current insights on bursitis were outdated and studies on bursitis associated with rheumatic inflammatory diseases are particularly lacking. Substantial overlap of enhanced expression of IL-6, IL-1β, TNF-α and infiltrating macrophages were found in bursitis irrespective of the underlying cause. In depth investigation on bursitis such as high throughput multi-omics are urgently needed to guide disease-specific therapeutic management.