Clinical characteristics and etiologies of hypomagnesemia in children: a single-center retrospective cohort study

To summarize the etiologies, clinical manifestations, and genetic profiles of children with hypomagnesemia admitted to the Department of Pediatric Endocrinology, Metabolism and Genetics (PEGM). A retrospective analysis was conducted on clinical data and genetic testing results of 28 children diagnosed with hypomagnesemia at our medical center between September 2018 and October 2025. Twenty-eight patients were included in the analysis. The median age at onset of the cohort was 9.28 (5.00, 12.30) years, and the median height standard deviation score (SDS) was − 1.28 (− 1.95, 0.11). This study involved Gitelman syndrome (GS) (11/28), HNF1B-related maturity-onset diabetes of the young (HNF1B-related MODY) (6/28), hereditary hypomagnesemia with secondary hypocalcemia (HSH) (3/28). Patients with HSH had the earliest onset and the lowest serum magnesium concentrations. Short stature was a common feature among patients with GS. HSH patients had fractional excretion of magnesium (FEMg) < 2%, while GS and HNF1B-MODY presented FEMg > 3% with renal magnesium loss. Metabolic alkalosis was detected in GS and HNF1B-MODY, but acid–base status remained normal in HSH. GS was characterized by hypocalciuria, whereas hypercalciuria occurred in hypoparathyroidism and Williams syndrome. All HNF1B-MODY patients exhibited some degree of renal structural anomalies on ultrasound. A total of ten genes and chromosomal microdeletions were identified: SLC12A3, MT-TF, MT-RNR1, TRPM6, HNF1B deletion, 17q12 deletion, 22q11.21 deletion, CASR, 7q11.23 deletion, and AIRE. Persistent hypomagnesemia in children attending the PEGM department is predominantly hereditary, with GS as the leading cause. Before genetic confirmation, differential diagnosis can be guided by renal magnesium excretion rate, blood gas analysis, calciuria evaluation, renal imaging, growth status, and clinical response to magnesium supplementation.