A male and female with juvenile metachromatic leukodystrophy (MLD) with unusual manifestations are presented, each involving a novel arylsulfatase A gene mutation. One patient demonstrated acute intermittent encephalopathic episodes for 1 year after having received the diagnosis of MLD at the age of 6 years. The other patient presented at the age of 5 years with acute hemiparesis, which was diagnosed as acute disseminated encephalomyelitis and resolved in 3 weeks. After 2 years of remission he started to show progressive neurological deterioration. The episodic manifestations in both patients were associated with acute, resolving cerebral lesions on magnetic resonance imaging accompanying or preceding the classical demyelinating lesions of MLD. The diagnosis of MLD was based on arylsulfatase A enzyme activity levels and genetic analysis, and after the exclusion of neurological conditions such as encephalitis, vasculopathy, or mitochondrial disorders. The pathogenesis of this previously undescribed finding in MLD is unknown but might be related to a susceptibility of myelin to acute damage.