Background/Purpose: the presence of other chronic inflammatory disease has been historically and academically thought to be “protective” conditions for the development of gout.

Objective: to evaluate the presence of concomitant chronic arthritis in patients with gout.

Methods: analysis of a dataset from a 20-year cohort of patients with gout prospectively included for follow-up. Diagnosis of associated rheumatic diseases at baseline or during follow-up were included if present. Classification criteria for such concomitant diseases varied depending on the classification criteria at the moment diagnosis was made.

Results: from 904 patients with 3,315 patient-year observation. Diagnosis of gout was based on crystal observation in 731 (80.8%). The number of patients and cumulated prevalence (n/%) of pyrophosphate arthritis (PPA), rheumatoid arthritis (RA), psoriatic arthritis (PsA) and spondyloarthritis (SpA) were 46/5.09, 5/0.55, 4/0.44, 3/0.33 respectively, very close to that expected in the general population. All patients with a diagnosis of both disease had crystal-proven gout (MSU crystals) or crystal (CPP)+X-ray proven PPA. Previous PPA was present in 3/46 patients, and both CPP and MSU crystals were observed in the same synovial fluid sample in 13/46, in the 23 left PPA appearing after properly controlled gout, no MSU crystals being observed in synovial fluid. Previous RA was present in 4/5 patients, previous PsA in 3/3, and previous SpA in 3/3. Only a patient developed RA 2-year after being satisfactorily treated for crystal proven gout, and showing high titers of RF and anti-CCP antibodies.Patients with PPA and RA showed higher age and more frequent chronic kidney disease than patients with PsA or SpA. Diuretic use, a risk factor for gout, was frequent in all groups (Table 1).

Conclusion:   the cumulated prevalence of other arthritis is as much in patients with gout as expected in the general population. Systematic analysis of synovial fluid samples, despite a previous and well established previous diagnosis allows to identify MSU and CPP crystals in patients suffering from other joint diseases but also to identify CPP crystals in patients with gout.