| Definition: |
A congenital nervous system abnormality characterized by severe to profound global developmental delay with inability to sit or walk independently, almost no cognitive development, poor visual fixation, and absent speech; progressive, severe microcephaly; and notable structural brain abnormalities apparent on brain imaging, including simplified gyral pattern, lissencephaly, partial or complete agenesis of the corpus callosum, enlarged ventricles, and cerebellar hypoplasia, that has_material_basis_in heterozygous mutation in the CRNKL1 gene on chromosome 20p11. |