Background/Purpose:

Gitelman syndrome (GS) is a rare recessively inherited tubulopathy, caused by inactive mutations in SLC12A3 gene encoding the thiazide-sensitive-sodium-chloride transporter. It is characterized by an hypokaliemic metabolic alcalosis with hypomagnesemia and hypocalciuria. Calcium pyrophosphate (CPP) crystals deposition is frequently described in cases-report GS but its prevalence and clinical phenotype are unknown.

Aims: to describe clinical, biological and radiological features of CPP in a cohort of patients with genetically proven GS.

Methods:

All patients (pts) with genetically proven GS in the French national reference center of rare diseases were proposed to have a consultation with a rheumatologic senior. Demographic data, history of joint pain and flare and biology disorders were recorded. Other causes of CPP disease were systematically ruled out. CPP crystal deposition was assessed by X-Ray (all peripheral joints and cervical spine) and ultrasonography (US) (wrists, knees, ankles and symptomatic joints). Patients with history of cervical pain underwent computed tomography (CT).

Results:

Forty-eight GS pts (20 men, mean age 46.6± 12.2 years) have been examined by a rheumatologist. Majority had a mutation on SLC12A3 gene. Forty pts experienced joint pain, 22 joint flare and 25 cervical pain. X-rays were performed in 40 pts, US in 34 and CT in 21. CPP depositions were observed in 34 (85.0%) pts, 26 (76.5%) and 15 (71.4%) by X-Ray, US and CT, respectively. They occurred in knees (n=25), wrists (n=19), cervical spine (n=17), shoulders (n=11), feet (n=10) and Achilles’ tendon or plantar fascia (n=11). CPP depositions were widespread involving at least 3 joints in 19 (55.9%) pts. In knees, CPP depositions involved meniscus (n=15), hyaline cartilages (n=8) and ligament or joint capsule (n=5). Cervical spine CT demonstrated CPP deposition in vertebral disc (n=12), transverse ligament (n=13), yellow ligament (n=6), vertebral facets (n=3) and temporo-mandibular joint (n=5). Pts with CPP crystal deposition were older (49.8 ± 11.1 vs 34.0 ± 10.0, p<0,01), more symptomatic and had lower magnesemia at consultation (0.60 ± 0.11 vs 0.75 ± 0.15 mM, p=0.029). CPP crystal deposition remained statistically correlated to serum magnesium level after age-adjustment. It was not associated with potassium level.

Table 1: Patients characteristics depending on the presence of CCP on radiographies

Conclusion:

CPP crystal deposition occurred in more than 80% of patients with GS, was widespread and often symptomatic. Most affected sites are wrists, knees and cervical spine. CPP crystal deposition was associated with long-standing GS, older age and low serum magnesium level. Further studies are necessary to understand how GS favors CPP crystal deposition.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/calcium-pyrophosphate-crystal-deposition-in-a-cohort-of-48-patients-with-gitelman-syndrome/