Inclusion Criteria: * Boys or girls with an early onset form of MLD. * Age between 6 months and 5 years, inclusive * Diagnostic of MLD based on the measurement of ARSA activity in leukocytes and the accumulation of sulfatides in urine, along with normal activity of at least one other sulfatase * Informed consent signed up and willingness for monitoring 2 years after treatment. * Normal values for standard laboratory tests Exclusion Criteria: * Absence of ARSA protein by immunocytochemistry and/or ELISA * Gestational age \<32 weeks of amenorrhoea and age \< 1 year * Brain atrophy with a subdural space \> 10 mm in the frontal region * Performance IQ\<50 at WPPSI-III or cognitive function \< 3rd percentile at the Bayley's test of infant development * If age \> 16 months at inclusion, inability to walk few steps alone OR inability to walk few steps with support on one side along with inability to stand up alone * Impossibility for anesthesia * Malignancy, cardiac malformation, liver dysfunction, or renal dysfunction * Neurological disorder, except benign, not related to MLD. * Any other clinically significant untreated co-morbid medical condition as determined by the clinical investigator, including cardiac, pulmonary or kidney disease. * MRI impossibility * Evoked potential impossibility * Participation to another therapeutic clinical trial for MLD. * Unaffiliated to any French or any other National Health Insurance.