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Megalencephalic leukoencephalopathy with subcortical cysts

Orpha number ORPHA2478
Synonym(s) MLC
Megalencephalic leukodystrophy
Megalencephaly - cystic leukodystrophy
Vacuolating megalencephalic leukoencephalopathy with subcortical cysts
Van der Knaap syndrome
Prevalence <1 / 1 000 000
Inheritance Autosomal dominant
Autosomal recessive
Age of onset Infancy
  • E75.2
  • C1858854
MeSH -
MedDRA -


Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a rare form of leukodystrophy. The phenotype consists of early onset ataxia followed by progressive signs of pyramidal tract involvement and mental deterioration. Prevalence is unknown, but the disease occurs more frequently in populations with high degree of consanguinity. Megalencephaly, appearing in the first year of life, is a characteristic feature of this syndrome. Magnetic resonance imaging (MRI) of MLC patients shows early and severe cerebral white matter involvement, despite relatively mild neurological findings during the early stages of the disease. In addition to a widespread T2 hyperintensity of the white matter, MRI shows T1 weighted and fluid attenuated inversion recovery (FLAIR) hypointense subcortical cysts in the temporal lobes and in the fronto-parietal subcortical areas. Overall, these severe neuroradiological abnormalities are concomitant with the clinical features, which are milder than those of other childhood leukodystrophie's forms. In the later stages of this disorder, cognitive impairment appears slowly, contributing significantly to the overall disability. Some patients show early onset learning disability starting during the first years of scholarship. MLC is an autosomal recessive inherited disease. Mutations in the MLC1 gene (22q13.33), coding for a protein whose function is unknown, were identified in MLC families of different ethnic background. Some patients do not harbor mutations in MLC1 and there is evidence of genetic heterogeneity in some sibships. No specific therapy is available for MLC. Management is based on physiotherapy procedures, psychomotor stimulation and treatment of seizures.

Expert reviewer(s)

  • Dr Clarice PATRONO

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Detailed information

Review article
  • EN (2011)
Clinical practice guidelines
  • DE (2012)
Clinical genetics review
  • EN (2012)
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