Calcium Pyrophosphate Crystal Deposition in a Cohort of 57 Patients with Gitelman Syndrome.

OBJECTIVE Gitelman syndrome (GS) is the most frequent salt-wasting genetic tubulopathy and a source of hypokalaemia and hypomagnesemia. Chondrocalcinosis (CC) is a frequent feature of GS. The aim of our study was to determine the prevalence, distribution patterns, clinical phenotypes and risk factors of CC in GS. METHODS This prospective study of a cohort of 57 patients with GS included a systematic screening for CC by peripheral joint radiography, cervical spine computerized tomography (CT) and joint ultrasonography. The prevalence of cervical C1-C2 CC by CT was compared between 33 GS patients and sex- and age-matched controls. Clinical and biochemical features were analysed to identify factors associated with CC. RESULTS Mean age of patients was 46.5 ± 12.4 years, 66.7% were women, and 93.0% carried SLC12A3 mutations. Mean serum magnesium level was 0.60 ± 0.30 mmol/l. CC was observed in 79% of patients, with the highest prevalence at the cervical spine (81.8%) followed by the knee (52.6%), wrist (50.9%), ankle (38.6%), temporomandibular joint (36.4%), shoulder (33.3%), hip (22.8%), elbow (14.0%) and sclero-choroid (12.1%). Prevalence of CC at the C1-C2 level was higher in the GS cohort than control group (72.7% vs 9.1%) (adjusted odds ratio 21.0, 95% CI 2.8-156.1, p= 0.003). Independent factors associated with CC were low serum magnesium level and age. CONCLUSION GS was associated with widespread CC, favoured by aging and hypomagnesemia. The C1-C2 level was the most affected site. Follow-up of this unique cohort will help understanding the clinical consequences of CC, especially the precise characterization of pyrophosphate arthropathy.