Case report: 'AARS2 leukodystrophy'

Pearls & Oy-sters: AARS2 Leukodystrophy-Tremor and Tribulations

A 35-year-old woman with a progressive, bilateral upper limb tremor, personality change, behavioral disturbance, and primary ovarian insufficiency was found to have AARS2-related leukodystrophy. She had congenital nystagmus which evolved to head titubation by age 8 years and then developed an upper limb tremor in her mid-teens. These symptoms stabilized during her 20s, but soon after this presentation at age 35 years, neurologic and behavioral disturbances progressed rapidly over a 12-month period requiring transition to an assisted living facility with care support (4 visits/day) and assistance for all activities of daily living. MRI of the brain demonstrated confluent white matter changes predominantly involving the frontal lobes consistent with a leukodystrophy. All other investigations were unremarkable. Nongenetic causes of a leukodystrophy including sexually transmitted diseases and recreational drug use were excluded. Family history was negative for similar symptoms. Gene panel testing identified compound heterozygous pathogenic AARS2 mutations. This case highlights the importance of MRI brain imaging in progressive tremor syndromes, the utility of gene panels in simultaneous testing of multiple disorders with overlapping phenotypes, and the need for awareness of comorbid endocrinological disorders in many of the genetic leukodystrophies, whose identification may aid in clinical diagnosis.

A Review of Brain and Pituitary Gland MRI Findings in Patients with Ataxia and Hypogonadism

The association of cerebellar ataxia and hypogonadism occurs in a heterogeneous group of disorders, caused by different genetic mutations often associated with a recessive inheritance. In these patients, magnetic resonance imaging (MRI) plays a pivotal role in the diagnostic workflow, with a variable involvement of the cerebellar cortex, alone or in combination with other brain structures. Neuroimaging involvement of the pituitary gland is also variable. Here, we provide an overview of the main clinical and conventional brain and pituitary gland MRI imaging findings of the most common genetic mutations associated with the clinical phenotype of ataxia and hypogonadism, with the aim of helping neuroradiologists in the identification of these disorders.

AARS2-Related Leukodystrophy: a Case Report and Literature Review

Mutations in the alanyl-transfer RNA synthase 2 (AARS2) represent a heterogenous group of autosomal recessive leukodystrophy characterized by cognitive decline, ataxia, spasticity, and Parkinsonism. AARS2-related leukodystrophy (AARS2-L) is extremely rare. To date, only 45 genetically confirmed cases, explaining the frequent diagnostic delay. Here, we report a 21-year-old male presented with unsteady gait and weakness in the bilateral lower extremities. Examination revealed dysarthria, cerebellar ataxia, paraparesis, and Parkinsonism with generalized hyperreflexia. MRI findings showed extensive white matter lesions in bilateral frontoparietal lobes, immediate periventricular regions, and corpus callosum. Focused exome sequencing revealed compound heterozygous mutations in the AARS2 gene confirming the diagnosis of AARS2-L; two heterogeneous missense mutations (c.452 T > C, p. M151T; c. 2557C > T, p. R853W) appeared together for the first time. We also reviewed phenotypic spectra of AARS2-related leukodystrophies from a total of 45 reported cases.

Gait Apraxia with Exaggerated Upper Limb Movements as Presentation of AARS2 Related Leukoencephalopathy

A 55-year-old male presented with apraxia of gait with exaggerated upper limb movement with relative preservation of cognition and mild spasticity of limbs. His investigations reveal posterior-predominant leukodystrophy in brain magnetic resonance imaging (MRI) and compound heterozygous mutations in mitochondrial alanyl-transfer RNA synthetase 2 (AARS2) by next generation sequencing. His asymptomatic brother also has MRI changes with subtle mild pyramidal signs. AARS2 mutation is a rare cause of mitochondrial encephalopathy which may give rise to leukodystrophy with premature ovarian failure, infantile cardiomyopathy, lung hypoplasia and myopathy. Gait apraxia as primary presenting feature of this rare variant of mitochondrial encephalomyopathy is hitherto un-reported.

Novel mitochondrial alanyl-tRNA synthetase 2 (AARS2) heterozygous mutations in a Chinese patient with adult-onset leukoencephalopathy

Background

Missense mutations in the mitochondrial alanyl-tRNA synthetase 2 (AARS2) gene are clinically associated with infantile mitochondrial cardiomyopathy or adult-onset leukoencephalopathy with early ovarian failure. To date, approximately 40 cases have been reported related to AARS2 mutations, while its genetic and phenotypic spectrum remains to be defined.

Case presentation

We identified a 24-year-old Chinese female patient with adult-onset leukoencephalopathy carrying novel compound heterozygous pathogenic mutations in the AARS2 gene (c.718C > T and c.1040 + 1G > A) using a whole-exome sequencing approach.

Conclusions

Our findings further extend the mutational spectrum of AARS2-related leukoencephalopathy and highlight the importance of the whole-exome sequencing in precisely diagnosing adult-onset leukoencephalopathies.

Insights Into the Role of CSF1R in the Central Nervous System and Neurological Disorders

The colony-stimulating factor 1 receptor (CSF1R) is a key tyrosine kinase transmembrane receptor modulating microglial homeostasis, neurogenesis, and neuronal survival in the central nervous system (CNS). CSF1R, which can be proteolytically cleaved into a soluble ectodomain and an intracellular protein fragment, supports the survival of myeloid cells upon activation by two ligands, colony stimulating factor 1 and interleukin 34. CSF1R loss-of-function mutations are the major cause of adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) and its dysfunction has also been implicated in other neurodegenerative disorders including Alzheimer’s disease (AD). Here, we review the physiological functions of CSF1R in the CNS and its pathological effects in neurological disorders including ALSP, AD, frontotemporal dementia and multiple sclerosis. Understanding the pathophysiology of CSF1R is critical for developing targeted therapies for related neurological diseases.

The emerging neurological spectrum of AARS2-associated disorders

BACKGROUND

The AARS2 gene encodes a mitochondrial alanyl-transfer RNA synthetase. Defects in this gene have been linked with autosomal recessive inheritance of a variety of different clinical phenotypes.

CASE

A 13 year-old boy developed behavioral and psychiatric problems following a mild head injury. At age 21 he developed tremor, parkinsonism, and eye nystagmus. MRI revealed white matter changes consistent with a leukoencephalopathy. Genetic studies revealed two pathogenic mutations in the AARS2 gene (c.647dupG and c.595C > T).

LITERATURE REVIEW

Only 47 cases of AARS2-associated disorders have been reported, with equal numbers of males and females, and age at onset ranging from infancy to 44 years. The most common clinical problems include movement disorders (71%), cognitive impairment (67%), corticospinal signs (64%), behavioral or psychiatric features (46%), and eye signs (34%). Imaging evidence suggestive of leukoencephalopathy is common, but not invariant. Premature ovarian failure is frequent in females, but not universal.

CONCLUSIONS

Defects in the AARS2 gene are a rare cause for a variety of movement disorders, often associated with brain imaging evidence suggestive of leukoencephalopathy.