RNASET2 (ribonuclease T2) is an enzyme which belongs to the RNase T2 family. It is highly expressed in the temporal lobe and fetal brain. RNASET2 gene is a novel member of the Rh/T2/S-glycoprotein class of extracellular ribonucleases. This protein can be inhibited by Zn2+ and Cu2+. It has ribonuclease activity, with higher activity at acidic pH and is probably involved in lysosomal degradation of ribosomal RNA. Defects in RNASET2 are the cause of leukoencephalopathy cystic without megalencephaly. An infantile-onset syndrome of cerebral leukoencephalopathy. Affected newborns develop microcephaly and neurologic abnormalities including psychomotor impairment, seizures and sensorineural hearing impairment. The brain shows multifocal white matter lesions, anterior temporal lobe subcortical cysts, pericystic abnormal myelination, ventriculomegaly and intracranial calcifications.