Abstract
Magnesium is one of the most abundant electrolytes in the human body but is often forgotten when it comes to the evaluation of an infant presenting with hypocalcemia. Its deficiency can present as neurological, cardiac and skeletal symptoms. Familial hypomagnesemia with secondary hypocalcemia is a rare autosomal recessive genetic disease caused by a transient receptor potential melastatin 6 gene pathogenic variant (TRMP6). The underlying defect lies in the intestinal absorption of magnesium. A delay in diagnosis and lack of timely initiation of treatment can lead to long term irreversible neurological complications and even death. We describe a case of an infant presenting with seizures and severe hypomagnesemia and hypocalcemia. Genetic analysis subsequently identified the abnormality as a frameshift mutation in the TRMP6 gene confirming the diagnosis of Familial hypomagnesemia with secondary hypocalcemia. With fewer than a hundred cases reported in the literature, we aim to highlight the importance of early diagnosis and treatment initiation and create a deeper understanding of the disease.