The correlation between vitamin D deficiency and hypocalcaemia in these neonates suggests that maternal vitamin D status may modify disease severity.<h4>Learning points</h4>TRPV6 mutations should be considered a rare cause of neonatal prenatal rickets and secondary hyperparathyroidism, even in the presence of normocalcaemic hyperparathyroidism. The gene discussed is TRPV6; the disease is Hypocalcemia.