Novel TRPM3 missense mutation leading to severe hypocalcemia presenting as seizures and complicated by non-sustained ventricular tachycardia: A case report.

Abstract

Background: Hypocalcemia is an electrolyte disorder that can be effectively corrected. However, in its severe form, it poses significant risks, including potentially fatal symptoms such as electrocardiographic changes that may lead to sudden cardiac arrest if not treated promptly.

Case presentation: We report the case of a young female patient who presented with multiple episodes of tonic posturing and altered level of consciousness. Diagnostic evaluation revealed severe hypocalcemia with hypomagnesemia, QT prolongation, and episodes of non-sustained ventricular tachycardia. The condition was managed with calcium and magnesium supplementation. Further investigations revealed a novel missense mutation in transient receptor potential melastatin 3 (TRPM3).

Discussion: Hypocalcemic seizures are rare in adults and are typically associated with severe hypocalcemia and cardiovascular instability, including ventricular dysrhythmias. The differential diagnoses in this case included primary hypoparathyroidism, Bartter syndrome type 5 (CaSR (calcium-sensing receptor) mutation), Gitelman syndrome, and claudin mutations. TRPM3 is highly expressed in kidney tissue, playing a role in the resorption of calcium and divalent ions. However, further research is needed to confirm its role in calcium homeostasis.

Conclusion: The patient was initially misdiagnosed with epilepsy for the past two years. Following a comprehensive evaluation, she was successfully treated with intravenous calcium and magnesium. On follow-up after six months, her condition showed marked improvement, characterized by better cardiac function and the absence of further seizure episodes. This case represents the first reported instance of a TRPM3 mutation affecting calcium channels, highlighting the need for further investigation into its implications for calcium metabolism.