Leukoencephalopathy due to autosomal recessive mutations in the mitochondrial alanyl-transfer RNA (tRNA) synthetase gene (AARS2-L)
Leukoencephalopathy due to autosomal recessive mutations in the mitochondrial alanyl-transfer RNA (tRNA) synthetase gene (AARS2-L) refers to a rare, adult-onset leukodystrophy 1. AARS2-L strongly resembles adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP).
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Epidemiology
Compared to ALSP, AARS2-L is even rarer and tends to present at a younger age, with a mean age of 26 years (14 to 44 years according to one study) 2.
Clinical presentation
Cognitive findings are invariably present and accompanied by motor and gait disturbances. Ovarian failure is seen in all female patients 1,2.
Pathology
Histopathologic findings are near-identical to those in ALSP. Therefore, a brain biopsy in the absence of the correct genetic test may be misleading 2.
Radiographic features
AARS2-L strongly resembles ALSP on imaging, but there are subtle differences 2-4.
CT
White matter calcifications, while often seen in ALSP, are not seen in AARS2-L.
MRI
Like ALSP, AARS2-L presents with brain volume loss and hyperintense changes on FLAIR and DWI in the periventricular and subcortical white matter. Compared to the more ’band- and dot-like’ white matter changes in patients with ALSP, white matter signal abnormalities typically appear more confluent in AARS2-L. The corpus callosum is always involved, and the pyramidal tracts also are more often involved than in ALSP. Atrophy is present to a lesser degree than in ALSP and the corpus callosum shows milder thinning.
T2/FLAIR: hyperintense
DWI: persistent DWI hyperintense white matter lesions are a typical finding, and, as opposed to ALSP, occur in all patients
T1: affected areas are low in signal
T1 C+ (Gd): no enhancement is visible
Treatment and prognosis
Currently, there exists no accepted specific therapy and thus treatment is supportive 5.
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