OP0183 Association between hfe genotypes and clinical severity characteristics of calcium pyrophosphate crystal arthritis

Background Several metabolic disturbances that reduce the activity of pyrophosphatases have been associated with development of calcium pyrophosphate crystal arthritis (CPPCA), but there is scarce data on their influence on clinical manifestations, as such disease-specific variables are not recorded in most available databases. Objectives To evaluate factors associated to severity of clinical joint involvement in patients with definite CPPCA. Methods Transversal study with prospective recruitment of cases (patients with CPPCA diagnosis confirmed by microscopy showing CPP crystals within leucocytes in synovial fluid plus presence of X-ray chondrocalcinosis in at least one joint) and controls (patients with synovial effusion shown to have no CPP crystals and no chondrocalcinosis in hands and knee X-rays), paired by age and gender. Patients with hemochromatosis or primary hyperparathyroidsm were not included. General variables were included along with plausible metabolic variables (Ca, P, Mg, iPth, iron saturation [satFe%], ferritin, diuretics and type of diuretic, and HFE genotype), and distributon of joint involvement (mono-oligo-polyarticular) and clinical manifestations (acute [A-CPPCA] and chronic inflammatory [CI-CPPCA]), as in EULAR recommendations. Results 340 patients and 316 controls were recruited, 53% were men, age at inclusion was 67±10 year (IC range 62–75), time from onset of symptoms 5.2±5.3 year (IC range 1–8). Regarding cases, A-CPPCA was present in 147 (43.2%), CI-CPPCA in 193 (56.8%), with monoarticular involvement in 102 (30.0%), oligoarticular in 176 (51.8%), and polyarticular in 62 (18.2%). Patients showed higher serum ferritine levels and lower Mg levels than controls (253 and 2.00 vs 204 and 2.08, respectively), along with higher rate of HFE gene mutations (Odds ratio 2.30, 95% CI: 1.66 to 3.20). Genotypes including homozygotic mutations of H63D allele, heterozygotic mutations for C282Y allele, and double heterozygotic mutations for C282Y and H63D were statistically associated with higher frequency of polyarticular involvement and with CI-PPA (figure 1). Clinical variables were also associated with higher SatFe% levels, but not Mg or ferritin levels. S65C gene mutations were not increased in patients compared to controls and did not show any association with clinical phenotype. Conclusions Patients with definite CPPCA show differences in serum Mg and Ferritin levels compared to that of controls, and may contribute, along with other factors, to development of CPPCA. Nevertheless, only presence of some HFE genotypes involving C282Y and H63D genes were associated with more severe phenotype of clinical involvement. Disclosure of Interest None declared