Cross-sectional study of 50 patients with calcium pyrophosphate dihydrate crystal arthropathy

Calcium pyrophosphate dihydrate crystal arthropathy (CPPA) is a well known but heterogeneous disease with a variable presentation and course. We present a cross-sectional study undertaken in a Portuguese rheumatology unit with the aim of analysing clinical and radiological patterns of CPPA in our population. The study population included 50 patients, 34 (68%) women and 16 (32%) men. The mean age was 69.8 +/- 8.8 years. The onset features were acute arthritis in 19 (38%) patients and chronic joint complaints in 26 (52%); five (10%) patients were asymptomatic at the time of diagnosis, which was based only on radiological findings. The diagnosis was established in 37 (74%) cases by clinical and radiographic features, in eight (16%) by clinical, X-ray and synovial fluid analysis, and in five (10%) by clinical features and fluid analysis. The disease course was characterised by acute episodic arthritis in 16 (32%) patients and by persistent symptoms (with or without synovitis) in 34 (68%). The pattern of CPPA in 20 (40%) patients was pseudo-osteoarthritis with synovitis, pseudo-osteoarthritis without synovitis in nine (18%), pseudogout in nine (18%), monoarthropathy in eight (16%) and pseudorheumatoid arthritis in four (8%). The phosphocalcium balance was altered in nine (18%) cases: six patients had hypercalciuria two hyperphosphaturia, two hypocalciuria, one hypophosphaturia and one hypercalcemia. Five patients had abnormal thyroid hormone levels, but only one presented with clinical hypothyroidism. Four patients showed increased parathormone levels, but only one presented with clinical hyperparathyroidism. Radiographic findings showed that 43 (86%) patients had meniscus calcifications, 20 (40%) radiocarpal and 16 (32%) calcification of the symphysis pubis. The study confirms the clinical variability of the disease in a population of Portuguese patients. The knee meniscus calcifications were the most sensitive single finding for establishing the diagnosis of CPPA. Almost all our patients had sporadic idiopathic CPPA without associated pathological conditions.