Introduction: To investigate the clinical and genetic characteristics of children with HSH caused by TRPM6 gene mutation.

Methods: Three patients were diagnosed as HSH in the department of neurology of Beijing children's hospital. Their clinical data, laboratory data and genetic testing results were retrospectively analyzed.

Results: In this group, there were 2 female and 1 male. The onset ages were 18d, 6m and 1m25d, respectively. The diagnosis was made at 4y2m, 8m and 11m respectively. Convulsive onset was observed in all 3 cases. All of them are mentally retarded and easily frightened. All had a severe decrease in blood magnesium (0.08 to 0.23mmol/L). All blood calcium was slightly decreased (1.67-1.81mmol/L). The parathyroid hormone was decreased in 2 cases (4.3-7.8pg/ml). Video electroencephalogram(VEEG) showed focal epileptic discharge in 1 patient (delayed diagnosis and treatment), and her cranial MRI showed mild brain atrophy. VEEG and cranial MRI were normal in the other 2 cases. TRPM6 gene mutation was detected in all 3 cases, including homozygous mutation in 1 case and complex heterozygous mutation in 2 cases. All the 3 children were treated with active magnesium supplementation. After the treatment, the symptoms of the three children all improved significantly. None of the 3 children had convulsive seizures.One child was mentally retarded, and two children were developing normally.

Conclusion/Discussion: HSH is a rare autosomal recessive hereditary disease. Early diagnosis and treatment of HSH can avoid brain injury and growth retardation.