gms | German Medical Science

Introduction: Calcium pyrophosphate deposition disease (CPPD), also known as pseudogout, is a prominent member of the crystal deposition diseases much like gout where urate crystals are the pathogens. CPPD differs from chondrocalcinosis, a radiographic finding showing joint calcification, which may or may not be relevant for the clinical picture of patients [1].

Methods: In a retrospective cross-sectional study design we reviewed the records of patients presenting to our center between 1.1.2016 and 31.03.2020 for diagnostic evaluation. Based on the availability of radiographs, 503 patients were identified including 181 with CPPD, 262 with rheumatoid arthritis (RA), 153 seropositive (58.4%) and 109 seronegative, 30 with gout and 30 with polymyalgia rheumatica (PMR). Radiographs of hands and feet of all patients and of the knee in 257 cases were read by two experienced readers who had no information on clinical data.

Results: Almost all patients had a short disease duration of < 1 year. In patients diagnosed with CPPD almost all radiographs showed chondrocalcinosis (95%) at some location, mostly in the hands. This was different in seronegative (33.1%) and seropositive (16.5%) RA. Chondrocalcinosis was also found less frequently in gout (12.1%) and PMR (13.5%), see Table 1 [Tab. 1]. Chondrocalcinosis in more than one joint was present in 61.7% patients with CPPD vs. 9.8% in seropositive and 20.9% in seronegative RA. Patients with CPPD were older and more often had acute attacks than RA patients. RA patients were more frequently treated with methotrexate, and patients with CPPD with colchicine.

Conclusion: There were a lot of similarities but also some important differences between patients with CPPD and RA with some differences between seropositive and seronegative RA. Of interest, radiographic chondrocalcinosis was seen in a third of seronegative RA patients but only in 16% of seropositive RA patients. Chondrocalcinosis in more than one joint occurs much more often in CPPD than in RA. Importantly, clinical symmetry of arthritis and involvement of hands did not differentiate between CPPD and RA, mainly the acuteness of attacks did. Co-occurrence of both diseases was frequently observed, and erosions were present in about half of the patients with RA but in only 28% with CPPD.

Disclosures: Hiermit erkläre ich, dass bei keinem der Autoren Interessenkonflikte bezüglich der hier beschriebenen wissenschaftlichen Arbeit vorliegen.