Progressive Ataxia with Elevated Alpha-Fetoprotein: Diagnostic Issues and Review of the Literature

ARV1 Gene: A Novel Cause of Autosomal Recessive Cerebellar Ataxia with Elevated Alpha Fetoprotein

ARV1 mutation is known to present as developmental and epileptic encephalopathy (DEE)-38. However, the phenotypic spectrum has been expanding ever since it was reported in 2016. Along with seizures and developmental delay, other unique clinical features include ophthalmological abnormalities and movement disorders in the form of ataxia and dystonia, especially in those with missense mutation. These manifestations closely mimic ataxia telangiectasia. Elevation of alpha-fetoprotein levels is an important investigative marker in the diagnosis of ataxia telangiectasia and ataxia with oculomotor apraxia syndromes. ARV1 can also be associated with increased alpha-fetoprotein. There are no reports evaluating alpha-fetoprotein levels in cases with ARV1 mutation, which is significant in the context of ocular abnormalities with ataxia. We report a case of ARV1 mutation presenting with ataxia, ocular abnormalities, and elevated alpha-fetoprotein levels, thus mimicking autosomal recessive cerebellar ataxias. This study provides a comprehensive literature review of the cases reported so far, thus expanding the understanding of the spectrum of presentation, and helps in correlating the clinical picture with the underlying causative genetic mutation. ARV1 gene is another example of one gene with phenotypic pleiotropy. Though presentation with DEE is common, a few, especially those with missense mutations, can present with ataxia and ocular abnormalities. All cases presenting with ataxia who have increased alpha-fetoprotein levels and seizures should be tested for the ARV1 gene, when testing for ataxia genes is negative. The underlying genetic mechanism can explain the varying clinical manifestations of the ARV1 gene.

The DNA repair enzyme, aprataxin, plays a role in innate immune signaling

Ataxia with oculomotor apraxia type 1 (AOA1) is a progressive neurodegenerative disorder characterized by a gradual loss of coordination of hand movements, speech, and eye movements. AOA1 is caused by an inactivation mutation in the APTX gene. APTX resolves abortive DNA ligation intermediates. APTX deficiency may lead to the accumulation of 5'-AMP termini, especially in the mitochondrial genome. The consequences of APTX deficiency includes impaired mitochondrial function, increased DNA single-strand breaks, elevated reactive oxygen species production, and altered mitochondrial morphology. All of these processes can cause misplacement of nuclear and mitochondrial DNA, which can activate innate immune sensors to elicit an inflammatory response. This study explores the impact of APTX knockout in microglial cells, the immune cells of the brain. RNA-seq analysis revealed significant differences in the transcriptomes of wild-type and APTX knockout cells, especially in response to viral infections and innate immune pathways. Specifically, genes and proteins involved in the cGAS-STING and RIG-I/MAVS pathways were downregulated in APTX knockout cells, which suggests an impaired immune response to cytosolic DNA and RNA. The clinical relevance of these findings was supported by analyzing publicly available RNA-seq data from AOA1 patient cell lines. Comparisons between APTX-deficient patient cells and healthy control cells also revealed altered immune responses and dysregulated DNA- and RNA-sensing pathways in the patient cells. Overall, this study highlights the critical role of APTX in regulating innate immunity, particularly in DNA- and RNA-sensing pathways. Our findings contribute to a better understanding of the underlying molecular mechanisms of AOA1 pathology and highlights potential therapeutic targets for this disease.

Evidence for pathogenicity of variant ATM Val1729Leu in a family with ataxia telangiectasia

Ataxia telangiectasia is a rare autosomal recessive multisystem disorder caused by mutations in the gene of ATM serine/threonine kinase. It is characterized by neurodegeneration, leading to severe ataxia, immunodeficiency, increased cancer susceptibility, and telangiectasia. Here, we discovered a co-segregation of two ATM gene variants with ataxia telangiectasia in an Egyptian family. While one of these variants (NM_000051.4(ATM_i001):p.(Val128*)) has previously been reported as pathogenic, the other one (NM_000051.4(ATM_i001):p.(Val1729Leu)) is regarded as a variant of uncertain significance. Our findings in this family provide additional evidence for causality of the second variant and argue that its status should be changed to pathogenic.

Inherited Neuromuscular Disorders: Which Role for Serum Biomarkers?

Inherited neuromuscular disorders (INMD) are a heterogeneous group of rare diseases that involve muscles, motor neurons, peripheral nerves or the neuromuscular junction. Several different lab abnormalities have been linked to INMD: sometimes they are typical of the disorder, but they usually appear to be less specific. Sometimes serum biomarkers can point out abnormalities in presymtomatic or otherwise asymptomatic patients (e.g., carriers). More often a biomarker of INMD is evaluated by multiple clinicians other than expert in NMD before the diagnosis, because of the multisystemic involvement in INMD. The authors performed a literature search on biomarkers in inherited neuromuscular disorders to provide a practical approach to the diagnosis and the correct management of INMD. A considerable number of biomarkers have been reported that support the diagnosis of INMD, but the role of an expert clinician is crucial. Hence, the complete knowledge of such abnormalities can accelerate the diagnostic workup supporting the referral to specialists in neuromuscular disorders.