Objective: To report the clinical manifestation and genetic characteristics of a child with Thiamine metabolism dysfunction syndrome 5.
Methods: Clinical data and genetic results were collected and analyzed. Peripheral blood samples of the child and their parents were collected for whole exome sequencing, and the functional effect of the variants on the TPK1 enzyme activity was verified by an in vitro assay.
Results: A four-year-old boy presented with preschool onset of ataxia were characterized. High-throughput sequencing identified a novel homozygous variant of TPK1 gene c.382G>A (p.Leu128Phe). His father and mother were both found carrying the variant. The variant protein showed a 30.9% reduction in TPK1 enzyme activity compared with the wildtype.
Conclusion: A novel pathogenic variant has been identified in a boy with thiamine metabolic dysfunction syndrome type 5.