BACKGROUNDHypomagnesemia with secondary hypocalcemia (HSH) is a genetic disorder arising from the body's impaired capacity to absorb and retain magnesium (Mg2+) consumed through diet. Consequently, Mg2+ levels in blood are significantly reduced, a condition referred to as hypomagnesemia. Insufficient levels of Mg2+ and calci-um (Ca2+) can lead to neurological complications that manifest during infancy, such as painful muscle spasms (tet-any) and seizures.METHODSWe reported a case of HSH involving a 10-year-old male patient from a Han Chinese family. He was admitted due to recurrent convulsions experienced over the past two years. The patient's initial episode occurred two years prior, when he collapsed without apparent cause and exhibited limb numbness, convulsions, and a disordered state of consciousness, accompanied by hypocalcemia. Cranial CT scans revealed multiple symmetrical calcifications in the basal ganglia, corona radiata, and cerebellar dentate nucleus.RESULTSDuring the hospital stay, the patient was administered the following treatments: Calcium Carbonate and Vitamin D3 Tablets (1.5 g of calcium carbonate and 125 IU of Vitamin D3 per tablet, 1 tablet/time) once daily, Calcitriol Soft Capsules (0.25 μg of calcitriol per capsule, 1 capsule/time) twice daily, Potassium Chloride Sustained-release Tablets (0.5 g of potassium chloride per tablet, 1 tablet/time) thrice daily, Potassium Aspartate and Mag-nesium Aspartate Tablets (158 mg of potassium aspartate and 140 mg of magnesium aspartate per tablet, 1 tablet/ time) thrice daily, and intravenous infusions of Magnesium Sulfate Injection (2.5 g/time) twice daily. After three days in the hospital, the patient's initial symptoms subsided, resulting in discharge with a prescription of ongoing oral medications including Calcium Carbonate and Vitamin D3 Tablets, Calcitriol Soft Capsules, and Potassium Aspartate and Magnesium Aspartate Tablets, with the same usage and dosage as the above three drugs. A month subsequent, the serum levels of Mg2+, Ca2+, potassium (K+), and phosphorus were 0.96 mmol/L, 2.52 mmol/L, 4.06 mmol/L, and 1.63 mmol/L, respectively.CONCLUSIONSPrimary HSH is an uncommon manifestation of parathyroid hypoplasia, clinically characterized by low levels of Mg2+, Ca2+, and K+ in the blood. Our findings serve to enrich and consolidate the knowledge for future case studies and follow-up investigations.