Primary hypomagnesemia with secondary hypocalcemia

Other Names: HOMG1; HSH; PHSH; Hypomagnesemic tetany; Hypomagnesemia caused by selective magnesium malabsorption; Hypomagnesemia intestinal type 1; Intestinal hypomagnesemia with secondary hypocalcemia

Familial hypomagnesemia with secondary hypocalcemia is a disease characterized by very low magnesium levels in the blood.

Cause

It is caused by mutations in the TRPM6 gene.

Inheritance

Autosomal recessive inheritance, a 25% chance

Inheritance is autosomal recessive.

Signs and symptoms

The disease begins during the first months of life with generalized and recurrent seizures which do not improve with usual treatment. Additional features include tetany (spasms of the hands and feet, cramps, spasm of the voice box (larynx), and overactive neurological reflexes), failure to thrive, restlessness, tremors, muscle spasms, and bluish skin around the mouth (perioral cyanosis). Abnormal heart rhythm (cardiac arrhythmia) may be observed. The low levels of magnesium result in low levels of parathyroid hormone (PTH) and in low levels of calcium in the bloods (hypocalcemia).

Diagnosis

PHSH is to be differentiated from these illnesses by the demonstration of a combination of the following findings; hypocalcemia refractory to calcium but responsive to magnesium, continuous requirement for magnesium supplementation to maintain normocalcemia, lack of hypermagnesiuria and/or impaired intestinal absorption of magnesium.

Treatment

Treatment involves giving magnesium, usually in the vein (intravenously), followed by life-long high-dose oral magnesium.

NIH genetic and rare disease info

• NIH info on Primary hypomagnesemia with secondary hypocalcemia

Primary hypomagnesemia with secondary hypocalcemia is a rare disease.