LIS1 duplication: expanding the phenotype.

Disruptions to LIS1 gene expression result in neuronal migration abnormalities. LIS1 heterozygosity is a significant cause of lissencephaly, while overexpression has recently been noted in cases of microcephaly, ventriculomegaly, and dysgenesis of the corpus callosum with normal cortical gyration. We report a partial LIS1 duplication in a child with microcephaly, neurodevelopmental delays, and profound white matter atrophy in the absence of overt lissencephaly. The duplicated genetic segment was contained entirely within the first intron of LIS1, a segment that often contains inducers of transcription. Normal gyral patterns with mild volume loss were observed at birth. Follow-up cranial imaging revealed further white matter loss, diminished sulcation, and ventriculomegaly, suggesting expanding hydrocephalus ex vacuo. The radiographic pattern has not been documented in the presence of a LIS1 gene abnormality, and suggests that altered expression of LIS1 has wider phenotypic manifestations than currently defined.