Identification of a rare homozygous SZT2 variant due to uniparental disomy in a patient with a neurodevelopmental disorder.

Because biallelic SZT2 variants have been reported in patients with neurodevelopmental disorders associated with various degrees of developmental delay, intractable seizures, and distinctive features; this condition is recognized as an autosomal recessive disorder. Previously, eleven patients have been reported and most of them have compound heterozygous SZT2 variants, leading to premature termination. In these patients, all reported variants were unique and there were no common pathogenic variants identified. In this study, we identified a paternal uniparental disomy of chromosome 1 in a patient with a neurodevelopmental disorder associated with severe intellectual disability, intractable epilepsy, autistic features, distinctive features, and transient macrocephaly. This resulted in homozygous patterns through chromosome 1. Among the variants in chromosome 1, a rare SZT2 variant, NM_015284.3:c.6553C>T (p.Arg2185Trp), was selected as a powerful candidate variant in this patient. Although the clinical features of this patient are relatively milder than that reported previously, it may be derived from genetic heterogeneity. This is the first report of a homozygous missense SZT2 variant.