Familial primary hypomagnesemia complicated with brain atrophy and cardiomyopathy.

A 2 5/12-year-old Chinese boy was investigated for refractory seizures and psychomotor regression. His birth history was unremarkable. Generalized seizures occurred at 2 weeks of age with hypocalcemia. They recurred at 7 months of age and have become aggravated since. During hospitalization, in addition to hypocalcemia and hypomagnesemia, he was found to have hypoparathyroidism, cardiomyopathy, and brain atrophy. Excessive renal loss of magnesium, general intestinal malabsorption, or inadequate dietary intake of magnesium were excluded. He was successfully treated with oral supplements of 19-25 mmole/day of magnesium. Over a few months, he made a dramatic progress in development. His hypoparathyroidism and cardiomyopathy gradually resolved. However, intermittent seizures and psychomotor retardation persisted up to his present age of 6 3/12 years. At 4 months of age his younger sister also developed seizures and was found to have isolated hypomagnesemia. This was corrected by oral magnesium and followed by resolution of the seizure. She has developed normally up to her present age of 1 10/12 years. Both patients are currently maintained on oral magnesium oxide.