An unusual cause of tetany in an infant born to a consanguineous couple with a sibling death

In this case report, we present an infant with abnormal body movements in her second month. She was born of a third-degree consanguineous marriage, and the previous sibling, who had similar complaints beginning in the fourth month, expired in the fifth month. On reviewing the video recorded by parents, the abnormal movements were suggestive of tetany. Biochemical investigations showed hypocalcaemia, hypomagnesaemia, hypoparathyroidism, normal urinary excretion of calcium and urinary magnesium losses. Intravenous calcium and magnesium corrections were given, and oral supplements were initiated. The genetic evaluation revealed a TRPM6 variant, a cause of intestinal hypomagnesaemia. The baby is currently thriving well on magnesium supplements.