Objectives
To estimate the prevalence of chondrocalcinosis and calcium pyrophosphate dihydrate deposition disease (CPPD) in patients with low alkaline phosphatase (ALP) levels and a positive ALPL genetic study (+GT) for hypophosphatasia (HPP) compared to those with the same biochemical abnormality and a negative genetic test (-GT). As a secondary objective, to analyze the biochemical factors associated with its presence in subjects with ALPL variants.
Methods
78 subjects with persistently low ALP levels and ALPL genetic test were included. Baseline and 24-month knee ultrasounds were performed in 42 + GT and 36 -GT subjects, in whom the fibrocartilage, hyaline cartilage of menisci, tendons and synovial fluid were scanned to detect calcium pyrophosphate deposits. A MyLabTwice ultrasound machine (Esaote, Genova, Italy) with a multifrequency linear array transducer (4-13 MHz) was used.
Results
A higher percentage of chondrocalcinosis was observed in the +GT group [9/42 (21.4%)] compared to the -GT group [2/36 (5.6%), P=.045)]. Two patients (4.76%), both in the +GT group, had arthritis secondary to CPPD. No new cases were identified at the 24-month control. When comparing +GT patients with and without chondrocalcinosis, ALP levels were lower and PLP and phosphate levels higher in the former group (P<.05). Logistic regression analysis revealed that higher PLP levels associated with the presence of chondrocalcinosis (OR: 1.1; 95% confidence interval, CI: 1.001-1.012).
Conclusions
Chondrocalcinosis was a frequent ultrasonographic finding in HPP. Arthritis secondary to calcium pyrophosphate deposits, however, proved less prevalent. Genetic causes, such as HPP, should be considered when evaluating patients with chondrocalcinosis in clinical practice.