OBJECTIVES:

Ataxia-Telangiectasia (A-T) individuals often present with respiratory muscle weakness, causing recurrent respiratory system infections, asthma-like symptoms, and chronic cough life-threatening events. The cough flow volume maneuver may reveal powerless airflow needed for efficient cough. The study aims to explore cough ability in relation to the flow/volume maneuver.

METHODS:

Data collected retrospectively from clinical charts of 35 A-T patients (age 12.7 ± 4.9 years) included forced expiratory and cough flow/volume maneuvers performed on the same day. Analysis compared among the maneuvers matching indices, numbers of cough-spikes, flow rate decay, and the reference data of similar ages. Adjusted to age, BMI, and number of hospitalizations prior to the tests, values were correlated with the cough indices.

RESULTS:

Cough peak-flow (C-PF) was propagated within 90 ± 20 ms compared with peak expiratory flow (PEF > 200 ms). C-PF measured values were higher than expiratory peak-flow measured values (3.27 ± 1.53 L/s versus 3.02 ± 1.52 L/s, respectively, but C-PF (%predicted) values were significantly lower than expiratory peak-flow (%predicted) (46 ± 15 versus 68 ± 20 %predicted, respectively, p < 0.002). The number of spikes/maneuver was low when compared with reference (2.0 ± 0.8 versus 6-12 spikes) and cough vital-capacity was lower than expiratory vital capacity (0.95 ± 0.43 versus 1.03 ± 0.47; p < 0.01). Inefficient C-PF was more prevalent in patients suffering from recurrent respiratory illness. The length of wheelchair confinement duration mostly influenced the C-VC level.

CONCLUSIONS:

The cough flow-volume curve can be applied as a method to follow cough ability in patients with A-T who showed a significantly reduced cough capacity. Further studies are needed to establish if the findings may aid decisions regarding cough assistance.

Ataxia-telangiectasia (A-T) is a rare multi-system disorder caused by mutations in the ATM gene. Significant heterogeneity exists in the underlying genetic mutations and clinical phenotypes. A number of mouse models have been generated that harbor mutations in the distal region of the gene, and a recent study suggests the presence of residual ATM protein in the brain of one such model. These mice recapitulate many of the characteristics of A-T seen in humans, with the notable exception of neurodegeneration. In order to study how an N-terminal mutation affects the disease phenotype, we generated an inducible Atm mutant mouse model (Atm(tm1Mmpl/tm1Mmpl), referred to as A-T [M]) predicted to express only the first 62 amino acids of Atm. Cells derived from A-T [M] mutant mice exhibited reduced cellular proliferation and an altered DNA damage response, but surprisingly, showed no evidence of an oxidative imbalance. Examination of the A-T [M] animals revealed an altered immunophenotype consistent with A-T. In contrast to mice harboring C-terminal Atm mutations that disproportionately develop thymic lymphomas, A-T [M] mice developed lymphoma at a similar rate as human A-T patients. Morphological analyses of A-T [M] cerebella revealed no substantial cellular defects, similar to other models of A-T, although mice display behavioral defects consistent with cerebellar dysfunction. Overall, these results suggest that loss of Atm is not necessarily associated with an oxidized phenotype as has been previously proposed and that loss of ATM protein is not sufficient to induce cerebellar degeneration in mice.

Ataxia-telangiectasia (AT) is a rare autosomal recessive disorder that is characterized by progressive cerebellar ataxia, telangiectasia, immunodeficiency, and a predisposition to leukemia/lymphoma. Here we report a rare case of lymphoma of the tongue accompanied by AT. Tumour extirpation was performed and diffuse large B-cell lymphoma was diagnosed following pathologic examination. A whole-body survey showed no other enlarged lymph nodes or tumour. The female patient then received a modified dosage of COPAD (cyclophosphamide, vinblastine, pirarubicin, and prednisolone) plus rituximab to avoid severe complications. As of follow-up after 3 years and 5 months, she remains in complete remission. Patients showing AT need careful surveillance and long-term continuous follow-up.

OBJECTIVES:

Defects in DNA damage responses or repair mechanisms cause numerous rare inherited diseases, referred to as "DNA-repair defects" or "DNA damage deficiency", characterized by neurodegeneration, immunodeficiency, and/or cancer predisposition. Early accurate diagnosis is important for informing appropriate clinical management; however, diagnosis is frequently challenging and can be delayed, due to phenotypic heterogeneity. Comprehensive genomic analysis could overcome this disadvantage. The objectives of this study were to determine the prevalence of ataxia-telangiectasia (A-T) and A-T-like DNA-repair defects in Japan and to determine the utility of comprehensive genetic testing of presumptively diagnosed patients in facilitating early diagnosis.

METHODS:

A nationwide survey of diseases presumably caused by DNA-repair defects, including A-T, was performed. Additionally, comprehensive next-generation sequencing (NGS) analysis, targeting known disease-causing genes, was conducted.

RESULTS:

Sixty-three patients with A-T or other diseases with characteristics of DNA-repair defects were identified. Thirty-four patients were genetically or clinically definitively diagnosed with A-T (n = 22) or other DNA-repair defects (n = 12). Genetic analysis of 17 presumptively diagnosed patients revealed one case of ataxia with oculomotor apraxia type 1 (AOA1); one ataxia with oculomotor apraxia type 2 (AOA2); two types of autosomal dominant spinocerebellar ataxia (SCA5, SCA29); two CACNA1A-related ataxias; one microcephaly with or without chorioretinopathy, lymphedema, or mental retardation (MCLMR); and one autosomal dominant KIF1A-related disorder with intellectual deficit, cerebellar atrophy, spastic paraparesis, and optic nerve atrophy. The diagnostic yield was 58.8%.

CONCLUSION:

Comprehensive genetic analysis of targeted known disease-causing genes by NGS is a powerful diagnostic tool for subjects with indistinguishable neurological phenotypes resembling DNA-repair defects.

Copyright © 2018 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

OBJECTIVES:

Ataxia telangiectasia (AT) is a rare autosomal recessive disorder caused by mutation in the Ataxia telangiectasia mutated (ATM) gene. This disorder is characterized by progressive cerebellar ataxia, telangiectasia, immunodeficiency and a predisposition to leukemia/lymphoma. In this study, we investigated a family with a new mutation in ATM, confirmed by molecular genetic test.

MATERIALS&METHODS:

Four members of a family including a symptomatic AT patient, his parents and sibling were examined for ATM gene defects at Kerman University Hospital, Kerman, Iran in 2016. DNA was extracted from peripheral leukocytes and the coding regions and exon-intron boundaries of ATM gene were amplified by next-generation sequencing technique. The identified mutation was tested in all members of the family.

RESULTS:

Molecular analyses identified a homozygous T to G substitution in c.7308-6 position resulting in a novel acceptor splice site in intron 49 of the ATM gene in the index patient. Parents and sibling of the proband were heterozygous for the same mutation.

CONCLUSION:

The variant c.7308-6T>G is predicted to be pathogenic due to impaired splice site causing exon skipping. This newly found frameshift mutation cosegregated as an autosomal recessive trait as expected for Ataxia telangiectasia syndrome.

DNA repair syndromes are heterogeneous disorders caused by pathogenic variants in genes encoding proteins key in DNA replication and/or the cellular response to DNA damage. The majority of these syndromes are inherited in an autosomal-recessive manner, but autosomal-dominant and X-linked recessive disorders also exist. The clinical features of patients with DNA repair syndromes are highly varied and dependent on the underlying genetic cause. Notably, all patients have elevated risks of syndrome-associated cancers, and many of these cancers present in childhood. Although it is clear that the risk of cancer is increased, there are limited data defining the true incidence of cancer and almost no evidence-based approaches to cancer surveillance in patients with DNA repair disorders. This article is the product of the October 2016 AACR Childhood Cancer Predisposition Workshop, which brought together experts from around the world to discuss and develop cancer surveillance guidelines for children with cancer-prone disorders. Herein, we focus on the more common of the rare DNA repair disorders: ataxia telangiectasia, Bloom syndrome, Fanconi anemia, dyskeratosis congenita, Nijmegen breakage syndrome, Rothmund-Thomson syndrome, and Xeroderma pigmentosum. Dedicated syndrome registries and a combination of basic science and clinical research have led to important insights into the underlying biology of these disorders. Given the rarity of these disorders, it is recommended that centralized centers of excellence be involved directly or through consultation in caring for patients with heritable DNA repair syndromes. Clin Cancer Res; 23(11); e23-e31. ©2017 AACRSee all articles in the online-only CCR Pediatric Oncology Series.

Ataxia Telangiectasia (A-T) is caused by biallelic inactivation of the Ataxia Telangiectasia Mutated (ATM) gene, due to nonsense or missense mutations, small insertions/deletions (indels), splicing alterations, and large genomic rearrangements. After establishing A-T clinicaldiagnosis, a molecular confirmation is needed, based on the detection of one of these loss-of-function mutations in at least one allele. In most cases, the pathogenicity of the detected mutations is sufficient to make a definitive diagnosis. More rarely, mutations of unknown consequences are identified and direct biological analyses are required to establish their pathogenic characters. In such cases, complementary analyses of ATM expression, localization, and activity allow fine characterization of these mutations and facilitate A-T diagnosis. Here, we present genetic and biochemical protocols currently used in the laboratory that have proven to be highly accurate, reproducible, and quantitative. We also provide additional discussion on the critical points of the techniques presented here.

ATM is a 350 kDa serine/threonine kinase best known for its role in DNA repair and multiple cellular homeostasis pathways. Mutation in ATM causes the disease ataxia telangiectasia (A-T) with clinical features including ataxia, severe cerebellar atrophy and Purkinje cell loss. In a cross-species study, using primary rat neurons, the roundworm C. elegans, and a mouse model of A-T, we showed that loss of ATM induces mitochondrial dysfunction and compromised mitophagy due to NAD⁺ insufficiency. Remarkably, NAD⁺ repletion mitigates both the DNA repair defect and mitochondrial dysfunction in ATM-deficient neurons. In C. elegans, NAD⁺ repletion can clear accumulated dysfunctional mitochondria through restoration of compromised mitophagy via upregulation of DCT-1. Thus, NAD⁺ ties together DNA repair and mitophagy in neuroprotection and intimates immediate translational applications for A-T and related neurodegenerative DNA repair-deficient diseases.