A case of megalencephalic leukoencephalopathy with subcortical cysts (van der Knaap disease): molecular genetic study.

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is an autosomal recessive disorder characterized by macrocephaly, deterioration of motor function with ataxia, spasticity and mental decline. It has been revealed that the mutations in the gene, KIAA0027, were responsible for MLC and the gene was renamed subsequently 'MLC1'. A 41-year-old Japanese male with MLC, in whom a homozygous missense mutation, TCG to TTG at codon 93 resulting in S93L, was detected in the MLC1 gene, was described. MRI revealed marked cerebral atrophy and enlargement of the ventricular system. The subject's motor function had severely deteriorated, while his cognitive function had maintained at the level of a 2-year-old for the past 10 years. The mutation in the MLC1 gene of the patient is considered to be a common mutation responsible for MLC in Japanese patients because the same mutation had been detected in two other Japanese patients with MLC.