Clinical management of primary hypomagnesemia with secondary hypocalcemia / 中华内分泌代谢杂志

Primary hypomagnesemia with secondary hypocalcemia(HSH) is a rare cause of hypoparathyroidism. This article presents a case of a 26-year-old male with recurrent generalized weakness and tetany, and a literature review of diagnosis and treatment of primary HSH. The biochemical tests revealed the patient had severe hypomagnesemia, mild hypocalcemia, hypokalemia, and hypoparathyroidism. Transient receptor potential melastatin-6(TRPM6) gene mutation were detected by gene test, which confirmed the diagnosis of primary HSH. The patient had been treated with long term oral magnesium supplementation, who remained asymptomatic during the follow-up. Primary HSH is a rare autosomal-recessive disorder caused by mutations in the TRPM6 gene which encoding a magnesium permeable channel expressed in the intestine and the kidney. The primary defect is impaired intestinal absorption of magnesium with secondary renal excretion, leading to a series of clinical symptoms. The treatment is mainly through lifelong magnesium supplementation.

Two cases of hereditary hypomagnesaemia with secondary hypocalcaemia and 4 novel mutations on TRPM6 gene / 中华实用儿科临床杂志

Objective To investigate the clinical,biochemical and genetic features of hereditary hypomagnesaemia with secondary hypocalcaemia.Methods Two boys came from different Chinese families.They were hospitalized at the Peking University First Hospital between 2014 and 2016 at the age of 9 years and 1 year and 2 months because of epilepsy and psychomotor retardation.Clinical investigation,laboratory examination,and medical imaging were performed for the etiological study.Whole-genome sequencing was used for the genetic analysis of the patients.Mutations of TRPM6 gene were confirmed by means of Sanger sequencing.Results Patient 1 presented with recurrent seizures and psychomotor retardation from the age of 3 months.Vision loss and psychomotor regression were noticed from the age of 9 years,accompanied with hypertension.Serum magnesium and total calcium were significandy decreased to 0.13-0.15 mmol/L and 1.43-2.00 mmol/L,respectively in patient 1.Serum potassium was reduced to 1.85-3.25 mmol/L.Blood parathyroid hormone was also decreased.On the TRPM6 gene of patient 1,2 novel non-sense mutations,c.2771G ＞ A (p.Trp924Ter) and c.115C ＞ T (p.Gln39Ter) were identified.Patient 2 presented with seizures and psychomotor retardation at the age of 2 weeks.Both of his serum magnesium (0.17-0.35 mmol/L) and serum total calcium (1.32-1.34 mmol/L) were significantly decreased.Blood parathyroid hormone was decreased.Two novel mutations (c.1239G ＞ A,p.W413X and c.146G ＞ A,p.C49Y) were found in the TRPM6 gene of patient 2.Severe hypomagnesaemia,hypocalcaemia and TRPM6 gene mutations confirmed the diagnosis of hereditary hypomagnesaemia with secondary hypocalcaemia in the 2 patients.After the large-dose supplement of magnesium sulfate,progressive clinical improvements were observed in the 2 patients.However,because of the severe brain damage,patient 1 still had psychomotor retardation.Patient 2 completely recovered.Conclusions Hereditary hypomagnesaemia with secondary hypocalcaemia is a severe inherited metabolic disease.Early diagnosis and large-dose magnesium supplement are the key to the good prognosis of the patients.In this study,2 Chinese children with the clinical onset of epilepsy and psychomotor retardation are reported.The diagnosis is made by way of blood biochemical assay and gene analysis.Four novel mutations on their TRPM6 gene are identified.