Megalencephalic leukoencephalopathy with subcortical cysts is a recessive autosomal genetic disorder, due to mutations in the gen megaloencephalic leukoencephalopathy with subcortical cyst 1 (MLC1) or hepatocyst cell adhesion molecule (HEPACAM). This white matter disease is characterized by macroencephaly of early onset, progressive motor or mental deterioration, ataxia and epileptic crises. Magnetic resonance imaging shows edema, diffuse compromise of the white matter and frontotemporal subcortical cysts. Here is the first case reported in Peru; it is a girl with clinical findings and typical findings disclosed in the nuclear magnetic resonance imaging in addition to heterocygotic mutations in the gen MLC1.