Clinical features and risk of recurrence of acute calcium pyrophosphate crystal arthritis.

OBJECTIVES: It is unclear whether attack recurrence rates are similar between acute calcium pyrophosphate (CPP) crystal arthritis and gout. This study compared the clinical features and recurrence rates of both conditions. METHODS: In this retrospective study, we reviewed 106 patients with acute CPP crystal arthritis (based on the presence of CPP crystals and/or chondrocalcinosis) and 173 patients with gout (based on the presence of monosodium urate crystals). We analysed clinical variables and compared them between the two conditions. We identified factors associated with the recurrence of acute CPP crystal arthritis. RESULTS: Patients with acute CPP crystal arthritis were older (76.5 vs. 62 years, p<0.001) and female (69.8% vs. 6.9%, p<0.001); they had a lower body mass index (22.3 vs. 23.7, p=0.002), lower renal insufficiency rate (27.4% vs. 41.6%, p=0.016), and higher rate of preceding infection (22.6% vs. 11.0%, p=0.009) than those with acute gout. Recurrence rates were similar between the groups (19.1% vs. 22.9%, p=0.562). Use of proton pump inhibitors (PPIs) [hazard ratio (HR), 5.625; 95% CI, 1.672-18.925; p=0.005] and warfarin (HR, 7.301; 95% CI, 1.930-27.622; p=0.003) or exposure to chemotherapy (HR, 5.663; 95% CI, 1.180-27.169; p=0.03) were associated with acute CPP crystal arthritis recurrence. CONCLUSIONS: Acute CPP crystal arthritis was more common than acute gout in older women with preserved renal function. Physicians should be aware of the association between recurrence and PPI, warfarin, or chemotherapy use in these patients.