Background Calcium Pyrophosphate Deposition Disease (CPPD) is a metabolic disorder caused by calcium pyrophosphate (CPP) formation in joints. The diagnosis of CPPD is based on clinical manifestations and/or the presence of chondrocalcinosis (CC) in combination with the detection of crystals in synovial fluid (SF). Current data shows that the frequency of CPPD could be underestimated, both be due to lack of examining of SF in patients with early or undifferentiated arthritis and the absence of accurate description of clinical signs, allowing us to suspect CPPD in pts.
Objectives The aim of the study was to describe the main characteristics of joint involvement in pts with CPPD diagnosed according to McCarty criteria and the presence of CPP crystals in SF.
Methods 101 pts consequently referred to our Institute during 2010-2012 ys with the presence of CPP crystals in SF were enrolled. 33 patients with mixed microcrystal deposition and 5 with rheumatoid arthritis were excluded from further analysis in order to describe the specific for CPPD joint involvement. Total 68 pts (43F/25M) with crystal-proven CPPD were analyzed. Mean age was 60 (28-83) ys, disease duration - 7,6 (0,3-29,2) ys. Crystal identification was performed using polarised light microscopy with compensator (Olympus CX31-P). X-ray of knees were performed in anterior-posterior and lateral projections, of the wrists – in anterior projection (Stephanix). US examination of knees and wrists was performed using Volusion-I (GE). US CPP crystal deposition features were taken as linear hyperechoic deposits in the hyaline and fibrous cartilage that was similar to roentgenological phenomenon of CC. US criteria of synovial hypertrophy (synovitis) were the visualization of hypoechoic intraarticular fixed, poor compressible tissue that has Doppler signal.
Results Joint involvement in CPPD manifested as coexistence of arthritis and arthralgia in different joints in 54% (n=37), arthralgia only in 36% (n=24) and arthritis only in 10% (n=7) of pts. In decreasing order presented arthritis of the wrists (15%), ankle (12%) and I MTP (6%) joints. In pts with arthritis only (n=7) more than a half (57%) had monoarthritis, 43% - oligoarthritis. There was the prevalence of oligoarticular involvement (66%) in pts with the combination of arthritis and arthralgia (n=37). Monoarthritis occurred to be in 23%, polyarthritis – in 11% of them. Arthralgia as well as arthritis predominantly developed in large joints. The combination of arthralgia more frequently occurred in the knee, shoulder, wrist, elbow and ankle joints. Additionally to clinical manifestations of CPPD we analyzed the frequency of revealing CC in the knee and wrists by X-ray and US and synovitis by US in pts. More than a half of pts without clinical manifestations of knee and wrist involvement had synovitis. Moreover, US appeared to be more informative than X-ray in revealing CC in the wrists (56% vs 17%, correspondingly, p=0,008). The usefulness of X-ray in detecting of CC both in arthritis and arthralgia of knees and wrists appeared to be the same.
Conclusions The knee occurred to be the target joint in CPPD both for arthritis and arthralgia. Acute arthritis of the I MTP or knee joint occurred in 18% of patients. Chronic arthritis was observed in 39% of patients with CPPD. US of the joints seem to be an informative imaging to detect CC, especially in the wrists. Moreover, US helped us to reveal synovitis in asymptomatic joints.
Disclosure of Interest None declared