MED23 and microcephaly: Indeed, besides the “classical phenotype” (i.e., microcephaly, axial hypotonia, spasticity, choreoathetosis, dystonia, and epilepsy), a number of additional signs including severe ID, speech delay, and brain anatomic defects (i.e., delayed myelination and thin corpus callosum) have sporadically been documented and emerged to be possibly the result of a pleiotropic effect of defective MED23 (6, 22).