Malignant prolongation of the QTc interval due to severe vitamin D deficiency: an unusual presentation.

Long QT syndrome with Torsades de Pointes (TdP) is a life-threatening polymorphic ventricular arrhythmia. The corrected QT (QTc) prolongation >500 milliseconds (ms) has been associated with TdP. Hypocalcaemia due to severe vitamin D deficiency is an uncommon cause of acquired long QT. We hereby present a case of a 40-year-old woman with sensorineural deafness and having symptoms of palpitations and presyncope. She had a QTc interval of 556 ms (reference range, QTc 451-470 ms in adult healthy woman) on 24-hour Holter analysis. Genetic analysis for congenital long QT syndrome was negative. She was diagnosed with severe hypocalcaemia secondary to severe vitamin D deficiency. After treatment with intravenous calcium gluconate, followed by oral vitamin D and calcium supplementation, the QTc became normalised and no further episode of palpitations or presyncope occurred. The causes of vitamin D deficiency was due to inadequate exposure to sunlight and a strict vegan diet.