[Causal relationship between gut microbiota and pigmented villonodular synovitis: a Mendelian randomization analysis].

OBJECTIVE: To investigate the causal relationship between gut microbiota and pigmented villonodular synovitis using Mendelian randomization analysis. METHODS: We conducted a two-sample Mendelian randomization analysis to investigate the causal relationship between 211 gut microbiome taxa and pigmented villonodular synovitis based on GWAS summary data, with inverse variance weighted (IVW) analysis as the primary result and the other methods as supplementary analyses. The reliability of the results was tested using Cochran's Q test, MR-Egger regression, MR-PRESSO method and conditional Mendelian randomization analysis (cML-MA). RESULTS: The increased abundance of Barnesiella (OR=3.12, 95% CI: 1.15-8.41, P=0.025) and Rumatococcaceae UCG010 (OR=4.03, 95% CI: 1.19-13.68, P=0.025) may increase the risk of pigmented villous nodular synovitis, and elevated abundance of Lachnospiraceae (OR=0.33, 95% CI: 0.12-0.91, P=0.032), Alistipes (OR=0.16, 95% CI: 0.05-0.53, P=0.003), Blautia (OR=0.20, 95% CI: 0.06-0.61, P=0.005), and Lachnospiraceae FCS020 group (OR=0.38, 95% CI: 0.15-0.94, P=0.036) and Ruminococcaceae UCG014 (OR=0.36, 95% CI: 0.14-0.94, P=0.037) were all associated with a reduced risk of pigmented villonodular synovitis, which were supported by the results of sensitivity analyses. Reverse Mendelian randomization analysis did not reveal any inverse causal association. CONCLUSION: Increased abundance of specific intestinal microorganisms is associated with increased or decreased risks of developing hyperpigmented villonodular synovitis, and gut microbiota plays an important role in the pathogenesis of this disease.

Diffuse pigmented villonodular synovitis in the metatarsophalangeal joint of the hallux: a case report.

UNLABELLED: A 60-year-old woman presented to our institution with a 2-month history of swelling and unrelieved pain on walking, localized to the right hallux. Magnetic resonance image scans revealed a multinodular soft tissue mass with low signal intensity on both T1- and T2-weighted images. Microscopic examination of a specimen procured using fine-needle biopsy revealed multinucleated giant cells, hemosiderin deposition, and foaming histiocytes, indicative of pigmented villonodular synovitis. Thereafter, excision of the mass and a thorough synovectomy were carried out using 2 separate longitudinal incisions. Although pigmented villonodular synovitis of the first metatarsophalangeal joint is not unheard of, it is relatively rare and physicians should consider it in the differential diagnosis when treating patients with prolonged chronic arthritis of the first pedal ray. This case, moreover, clearly depicts the diagnostic value of magnetic resonance imaging combined with fine-needle biopsy in regard to making the diagnosis of pigmented villonodular synovitis. LEVEL OF CLINICAL EVIDENCE: 4.