ICD-10 Code G93.42 – Megalencephalic leukoencephalopathy with subcortical cysts (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G93.42 – Megalencephalic leukoencephalopathy with subcortical cysts
What it is
Megalencephalic leukoencephalopathy with subcortical cysts is a rare inherited white-matter disorder. It causes enlarged brain size and characteristic cysts near the brain’s outer regions.
Clinical signs
Clinical features often include early-onset macrocephaly, delayed motor development, and progressive neurologic impairment. Seizures, ataxia, and spasticity may occur; clinical features vary, so refer to documentation.
When to use this code
Use G93.42 when the provider documents megalencephalic leukoencephalopathy with subcortical cysts, also known as MLC. Apply it for confirmed diagnoses based on imaging, genetics, or specialist assessment. Do not code it from nonspecific white-matter disease alone.
Do not use for
Do not use this code for general leukodystrophy, hydrocephalus, or isolated macrocephaly without the documented syndrome. Check documentation if the record does not clearly identify subcortical cysts.
Coding tip
Match the code only to a documented MLC diagnosis and verify that the chart supports the specific subtype.