Both the juvenile and adult-onset forms are distinguished from late infantile MLD by slower progression, higher residual ARS-A activity, and a preponderance of neuropsychiatric abnormalities, including conduct disorder, nonverbal learning disability, alcohol or substance abuse, depression, and schizophrenia-like psychosis.
+3,+7,+8 Baumann et al.
+7 described two distinct clinical patterns of adult MLD.
+7 One presents with predominantly motor manifestations similar to those found in infantile cases. The other presents as a schizophrenia-like psychosis, with prominent negative signs (e.g., psychomotor slowing, apathy, apragmatism, poor judgment, and disorganized thinking). The cognitive profile resembles a subcortical dementia, including impaired verbal fluency, impaired memory retrieval, and executive dysfunction. Disinhibition, anosognosia, complex delusions, bizarre behavior, and auditory hallucinations may also occur.
+7,+9 Extrapyramidal symptoms, including choreoathetosis and dystonia, seizures, and peripheral neuropathy rarely occur. Some variability is probably related to different mutations within the ARS-A gene. For example, adult MLD patients with primarily psychiatric manifestations may carry mutations in regions of the ARS-A gene that are distinct from the common P426L mutation found in most patients with motor signs.
+7 However, strict genotype-phenotype correlations do not apply in all cases, and genetic background probably modifies the clinical profile.
+4 Whatever the age of onset, progression is the rule. Motor signs can be absent until decades into the illness despite the characteristic white matter appearance on neuroimaging.
+10 The prominent behavioral disturbance and more subtle initial cognitive dysfunction combined with the lack of motor signs can make recognition of this degenerative dementia challenging. All cases eventually manifest dementia and spasticity.