Bone Abstracts

Background: Dilated cardiomyopathy is the leading cardiac cause of death in children. Treatment options include heart transplantation. Reversible causes are rare but hypocalcaemia secondary to vitamin D deficiency is a recognised cause and presents during infancy in at risk populations. Risk factors include babies who were breast fed, dark skinned and from mothers with vitamin D deficiency. We present an unusual case of vitamin D replete, hypocalcaemic cardiomyopathy secondary to 1 α hydroxylase deficiency, which has not previously been described.

Presenting problem: A 4 month-old baby, born to consanguineous parents of Indian origin, presented acutely with poor feeding and shortness of breath. Chest x-ray showed an enlarged cardiac shadow and severe skeletal changes suggestive of rickets. He was found have dilated cardiomyopathy with severely compromised systolic function and left ventricular ejection fraction of 25%. He proceeded to have two hypocalcaemia seizures and bloods showed a low plasma corrected calcium level of 1.4 mmol/l, phosphate of 1.7 mmol/l, magnesium of 0.7 mmol/l and elevated PTH of 83.5 pmol/l. Although his mother had low vitamin D of 38 nmol/l, he had a normal vitamin D level of 96 nmol/l and had not been breast fed but given infant formula since birth.

Clinical management: The baby was commenced on intravenous calcium supplementation, oral phosphate, magnesium, oral cholecalciferol and alfacalcidol. Shortly after treatment was initiated, serum 25 vitamin D levels were 199 nmol/l with paired 1.25 vitamin D levels being inappropriately low at 43 pmol/l (48–145) suggesting a diagnosis of 1.25 hydroxylase deficiency. After doubling the dose of alfacalcidol, the intravenous calcium requirement could be reduced and finally discontinued 4 weeks after presentation. This child’s dilated cardiomyopathy was managed with diuretics, digoxin and capropril. Although initially the child was considered for transplantation, the left ventricular dysfunction resolved and on discharge the left ventricular shortening fraction was 30%, within normal limits.

Discussion: Reversible causes of dilated cardiomyopathy are important to diagnose. Although vitamin D deficiency is the commonest during infancy, other causes of hypocalcaemia may also adversely affect cardiac function and must be considered. We present an unusual case of reversible hypocalcaemic dilated cardiomyopathy secondary to 1 α-hydroxylase deficiency.

Disclosure: The authors declared no competing interests.