Higher Rates of Psoriatic Arthritis in Patients with Calcium Pyrophosphate Deposition Disease than in Controls: A Retrospective Cohort Study

Calcium pyrophosphate deposition disease (CPPD) has been shown to be associated with inflammatory arthritis such as rheumatoid arthritis. However, few studies have investigated the correlation between CPPD and psoriatic arthritis (PsA). Our study aimed to determine whether there were higher rates of PsA in patients with CPPD than controls. A retrospective cohort study was conducted using the Veterans Affairs’ Corporate Data Warehouse. Individuals with a CPPD ICD code were matched with controls and diagnoses of PsA and psoriasis were collected. A total of 41,084 CPPD patients were matched with 119,192 controls. The proportion of CPPD patients with PsA diagnosis was more than double that of controls (1.07% vs. 0.37%; p < 0.0001), and more CPPD patients were diagnosed with psoriasis (3.05% vs. 2.52%; p < 0.0001). Those with CPPD had higher odds of a PsA diagnosis (OR 3.550, 95% CI 2.602–4.844). A total of 61.59% of PsA diagnoses preceded the CPPD diagnoses by at least one year. This is the first case–control study demonstrating an association between CPPD and PsA, potentially related to the fact that both PsA and CPPD could be triggered by trauma, and are closely associated with osteoarthritis. It also is possible that inflammatory pathways contribute to CPP crystal deposition in joints.