Teaching NeuroImages: A child with macrocephaly and psychomotor development delay

A 12-month-old boy, born to consanguineous parents, presented with developmental delay and macrocephaly. MRI revealed diffuse cerebral white matter T2 hyperintensity and temporal subcortical cysts (figure), leading to a diagnosis of megalencephalic leukoencephalopathy with subcortical cysts (MLC). Diffuse white matter changes and temporal subcortical cysts are hallmarks of this rare disorder1,2; these features, in addition to the lack of basal ganglia involvement, distinguish MLC from other leukodystrophies.1 MLC is caused by MLC1 or GLIALCAM mutations leading to a defect of brain ion and water homeostasis.2 Clinical features include macrocephaly, mild developmental delay, and easily controlled seizures.1