Disease Heterogeneity in Na+/Citrate Cotransporter Deficiency.

We report a novel mutation found in two siblings, a male and a female aged 8 and 5 years, respectively. Both patients presented with developmental delay and intractable seizures consistent with previous reports of SLC13A5 transporter deficiency. Both had two mutations in the SLC13A5 gene, c.655G>A (G219R) and the novel mutation c.245A>G (Y82C). However, the phenotypes were not identical as the female had focal cortical dysplasia that led to brain surgery. This is another example of the heterogeneity in disease expression even when the genotype is identical in the affected individuals.