G93.42
BillableMegalencephalic leukoencephalopathy with subcortical cysts
HCC Category Mapping
V28HCC 200 — Cerebellar Ataxia and Other Degenerative Diseases of Nervous System
0.262What This Code Means
A rare inherited brain disorder characterized by abnormal brain enlargement and white matter changes with fluid-filled cysts.
Coding Tips
- •This is a rare genetic leukodystrophy; ensure imaging findings confirm the diagnosis before coding
- •Document family history and genetic testing results when available
Clinical Significance
Megalencephalic leukoencephalopathy with subcortical cysts is a rare inherited white matter disorder typically presenting in early childhood with macrocephaly and progressive neurological decline. The condition causes progressive loss of motor and cognitive function due to extensive white matter vacuolization and subcortical cyst formation. This is a significant chronic neurological condition requiring lifelong management and support services.
Documentation Requirements
- ✓MRI demonstrating diffuse white matter signal abnormality with characteristic subcortical cysts, particularly in temporal regions
- ✓Genetic testing confirming mutations in MLC1 or GLIALCAM genes when available
- ✓Documentation of macrocephaly onset, typically in first year of life
- ✓Neurological examination documenting progressive motor and cognitive deficits
- ✓Current functional status and supportive care plan
Commonly Confused Codes
G93.43 — Leukoencephalopathy with calcifications and cysts: different pathology with calcifications rather than the MLC patternG93.44 — Adult-onset leukodystrophy with axonal spheroids: adult onset and different genetic basis (CSF1R)G90.B — LMNB1-related autosomal dominant leukodystrophy: different gene, adult onset, autosomal dominantE75.25 — Metachromatic leukodystrophy: lysosomal storage disorder with different enzyme deficiency
Code Hierarchy
└G93Other disorders of brain└G93.4Other and unspecified encephalopathy└G93.42Megalencephalic leukoencephalopathy with subcortical cysts
└G93.42Megalencephalic leukoencephalopathy with subcortical cysts