ESPE Abstracts

Introduction: Congenital hypomagnesaemia is a rare autosomal recessive disease presenting with convulsions in the newborn period. Early diagnosis and treatment are required if neurodevelopmental delay is to be prevented.

Materials and Methods: Retrospective study of patients with congenital hypomagnesemia followed in our department.

Objective: To document the clinical presentation, diagnosis and outcome according to the age of onset of definitive treatment in patients with congenital hypomagnesemia.

Results: Four patients (3M/1F) from four separate families, all consanguineous, were studied. A girl from one family had died previously aged eight months following a convulsive seizure and two maternal cousins from another family were being followed for hypomagnesemia. Presentation in all four patients was with hypocalcaemic convulsions. Age at diagnosis of hypocalcaemia vs age at recognition of hypomagnesemia was as follows: Patient (Pt) 1 - 21 days vs 21 days; Pt 2 - 28 days vs 2 months; Pt 3 - 2 months vs 3 months; and Pt 4 - 40 days vs 40 days. Serum magnesium at diagnosis ranged between 0.03 and 0.4 mmol/L. All patients were treated initially with magnesium and calcium. Calcium was subsequently discontinued in in all but one. At follow up Pt 1 was aged 2.4 years with normal development. Pt 2 was aged 6.8 years, with good school performance. Pt 3 was aged 2.5 years, continued to experience convulsions despite treatment and was showing developmental delay. Pt 4 was aged 7.2 years and despite her relatively early diagnosis, also continues to convulse with evidence of frontotemporal cortical atrophy, attributable to poor adherence to treatment. Genetic studies were unavailable for any of the four families.

Discussion: The clinical presentation in our families, with parental consanguinity and hypocalcaemia secondary to hypomagnesemia renders a defect either in intestinal magnesium absorption (mutation of the gene encoding TRPM6) or of renal origin (mutation of the CLDN16 gene) highly likely. Our experience underlines the importance of measuring magnesium in newborn infants with hypocalcaemia, especially when there is parental consanguinity and when the convulsions do not subside with conventional calcium treatment. Ideally, index patients with congenital hypomagnesemia should undergo genetic testing to enable prenatal diagnosis and early magnesium treatment in future siblings, and thus avoid postnatal convulsions with death and neurodevelopmental delay.