Three cases of hereditary hypomagnesemia with secondary hypocalcemia caused by novel TRPM6 gene mutations and a literature review
Mengjie Yang, Zhichao Zheng, Xiaoou Shan, Yue LuoAbstract
Objectives
Hereditary hypomagnesemia with secondary hypocalcemia (HSH), also referred to intestinal hypomagnesemia 1 (HOMG1), is an extremely rare autosomal recessive genetic disorder with an unclear incidence rate. To summarize the clinical phenotypes and genetic characteristics of Chinese patients with HSH caused by TRPM6 gene mutations.
Case presentation
Three Chinese children in our center presented with afebrile convulsions, one of them developed gross hematuria. These three patients carried a total number of four novel TRPM6 mutations: c.4599C>G, c.274A>G, c.517T>A, and c.5135-1G>A. Among the 30 Chinese HSH patients, 21 were male and 9 were female. The median age of onset was 5.50 (2.00, 10.25) months. The average serum magnesium level increased from 0.24 ± 0.13 mmol/L before treatment to 0.57 ± 0.10 mmol/L after treatment. The main clinical symptom was convulsions (90.0 %), predominantly afebrile convulsions. Developmental delay was observed in 23.3 % of patients, and 36.7 % had normal electroencephalogram and brain MRI findings.
Conclusions
HSH primarily presents with convulsions in infancy. For patients of different ages with unexplained recurrent convulsions or tetany, if the fractional excretion of magnesium (FEMg) is ≤2 %, HSH should be considered as a primary diagnosis.