Thick Corpus Callosum: An Unusual Finding of TUBGCP2-Related Tubulinopathy

Tubulinopathies are a group of neurologic disorders caused by mutations in tubulin-related genes, characterized by a broad spectrum of cortical malformations. These disorders are typically associated with a thin or normal corpus callosum, while a thick corpus callosum has been rarely documented. This study reports the first known case of a homozygous insertion variant in the TUBGCP2 gene associated with a thick corpus callosum. A 2-year-old male of Turkish origin presenting with microcephaly, developmental delay, distinctive facial features, and hypertonia. Brain MRI revealed cortical malformations consistent with the pachygyria-polymicrogyria complex, as well as a thickened corpus callosum. Exome sequencing identified a homozygous NM_006659.4:c.2647dupC p.(Gln883Profs*62) variant in the TUBGCP2 gene, which was confirmed by Sanger sequencing. This case expands both the genotypic and phenotypic spectrums of TUBGCP2-related tubulinopathies by reporting a homozygous TUBGCP2 variant in a patient with a thick corpus callosum, suggesting that TUBGCP2 variants may influence corpus callosum morphology in a more variable manner than previously understood.