Biallelic KCTD3 nonsense variant derived from paternal uniparental isodisomy of chromosome 1 in a patient with developmental epileptic encephalopathy and distinctive features

A biallelic nonsense variant of the potassium channel tetramerization domain-containing protein 3 gene (KCTD3) [c.1192C>T; p.R398*] was identified in a patient with developmental epileptic encephalopathy with distinctive features and brain structural abnormalities. The patient showed isodisomy of chromosome 1, where KCTD3 is located, and the father was heterozygous for the same variant. Based on these findings, paternal uniparental disomy was considered to cause the biallelic involvement of KCTD3.