The pleiotropic nature of the clinical phenotypes of patients with ataxia-telangiectasia (A-T)--which encompass cerebellar degeneration (leading to ataxia), gonadal atrophy, and cancer predisposition--suggests multiple functions of the gene responsible for the disease. The ataxia-telangiectasia mutated gene product (ATM), whose loss of function is responsible for ataxia-telangiectasia, is a protein kinase that interacts with several substrates and is implicated in mitogenic signal transduction, chromosome condensation, meiotic recombination, cell-cycle control and telomere maintenance. This review focuses on the critical roles that ATM appears to play in cell-cycle checkpoints, DNA repair, telomere metabolism and oxidative stress, indicating how defects in these processes might lead to ataxia-telangiectasia.

Much progress has been made in the early diagnosis of ataxia-telangiectasia since the gene was cloned in 1995, A clinical diagnosis can now be confirmed by radiosensitivity testing (colony survival assay), immunoblotting, and mutation detection. The diagnostic value of serum alpha-fetoprotein levels and radiosensitivity has been reevaluated using patients with diagnoses based on the presence of mutations in the ATM gene and the absence of ATM protein in nuclear extracts. Little progress has been made in treating the progressive ataxia.

Ataxia-Telangiectasia (A-T) is a genetic condition leading to neurological defects and immune deficiency. The nature of the immune deficiency is highly variable, and in some cases causes significant morbidity and mortality due to recurrent sinopulmonary infections. Although the neurological defects in A-T are progressive, the natural history of the immune deficiency in A-T has not been evaluated formally. In this study we analyse the clinical history and immunological data in 44 patients with A-T who attended the National Ataxia-Telangiectasiaclinic in Nottingham between 2001 and 2011. Using patient medical records and Nottingham University Hospitals (NUH) National Health Service Trust medical IT systems, data regarding clinical history, use of immunoglobulin replacement therapy, total immunoglobulin levels, specific antibody levels and lymphocyte subset counts were obtained. T cell receptor spectratyping results in some patients were already available and, where possible, repeat blood samples were collected for analysis. This study shows that subtle quantitative changes in certain immunological parameters such as lymphocyte subset counts may occur in patients with A-T over time. However, in general, for the majority of patients the severity of immune deficiency (both clinically and in terms of immunological blood markers) does not seem to deteriorate significantly with time. This finding serves to inform the long-term management of this cohort of patients because, if recurrent respiratory tract infections present later in life, then other contributory factors (e.g. cough/swallowing difficulties, underlying lung disease) should be investigated aggressively. Our findings also offer some form of reassurance for parents of children with A-T, which is otherwise a progressively severely debilitating condition.

Ataxia telangiectasia (AT) is an autosomal‐recessive, multisystem disease characterized by progressive neurologic decline, oculocutaneous telangiectasias, immunodeficiency, susceptibility to sinopulmonary infections, autoimmune or other chronic inflammatory diseases, radiation sensitivity (x‐rays and γ‐rays), and malignancies.1, 2 It is caused by a mutation in the ataxia telangiectasia mutated (ATM) gene located on chromosome 11q22‐23.3 In typical cases, progressive ataxia starts in the first year of life, leads to a wheelchair‐bound state around the second decade, and it is variably accompanied by other movement disorders like chorea, dystonia, or myoclonus.1 However, there is increasing evidence of atypical forms or variants in which the clinical picture is different, in that it is less severe, with dystonic‐predominant symptoms and without the typical clinical of AT.

https://onlinelibrary.wiley.com/page/journal/23301619/homepage/mdc312564-sup-v001_1.htm.

Advances in genetic testing have led to the identification of multiple genes associated with a hereditary risk for developing breast and other cancers. One such gene is the ataxia telangiectasia mutated (ATM) gene, which is available on many genetic panels offered to individuals with suspected hereditary risk. Genetic testing can often lead to improved understanding and clarification of risk for developing cancer, as well as allow affected individuals to make informed choices about management, including the adoption of primary prevention strategies and more aggressive screening than typically recommended in the general population. This article provides an overview of the role of mutations in the ATM gene in developing malignancies, along with emerging research on treatment implications based on genetic testing results.
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A 25-year-old man was admitted to the Department of Neurology, Gunma University Hospital, in June 1997. He had an intellectual disability and had suffered from repeated infection since childhood. Cerebellar ataxia had developed at 19 years of age and he had been clinically diagnosed with ataxia telangiectasia (AT) comprising cerebellar ataxia and oculocutaneous telangiectasia at 24 years of age. He died from pneumonia and renal failure at 26 years of age. Neuropathological examination revealed Purkinje cell loss and atrophy of the dentate nuclei in the cerebellum, anterior horn-cell atrophy and demyelination of the gracile fasciculi in the spinal cord, and the existence of nucleocytomegalic cells in the anterior pituitary gland. These neuropathological findings correlated with previously reported cases of AT. In addition, spongy degeneration was found, predominantly around the blood vessels in the cerebral cortex. Diffuse spongy degeneration and multiple foci of coagulative necrosis with calcification were noted in the white matter. Abnormal vasculature was noted in both degenerative and necrotic areas in the cerebral cortex and in the white matter. The vessels at the center of the areas of spongy degeneration in the cerebral cortex had irregularly arranged and enlarged smooth-muscle-cell nuclei and a distorted, narrow lumen. The vessels present in the white matter were hyalinized. To our knowledge, these vascular abnormalities in the brain parenchyma have not been reported previously.

Ataxia telangiectasia (A-T) results from inactivation of the ATM protein kinase. DNA-damage signaling is a prime function of this kinase, although other roles have been ascribed to ATM. Identifying the primary ATM function(s) for tissue homeostasis is key to understanding how these functions contribute to the prevention of A-T-related pathology. In this regard, because A-T is primarily a neurodegenerative disease, it is essential to understand how ATM loss results in degenerative effects on the nervous system. In addition to delineating the biochemistry and cell biology of ATM, important insights into the molecular basis for neurodegeneration in A-T come from a spectrum of phenotypically related neurodegenerative diseases that directly result from DNA-repair deficiency. Together with A-T, these syndromes indicate that neurodegeneration can be caused by the failure to appropriately respond to DNA damage. This review focuses on defective DNA-damage signaling as the underlying cause of A-T.

This article summarizes evident and recent findings on the characteristics of the neurological phenotype in ataxia telangiectasia (AT), reviews neuropathological and neuroradiological findings, and outlines therapeutic treatment options. In addition, this review offers an overview of current hypotheses on mechanisms of neurodegeneration in AT and discusses their relevance in clinical neurology. The obvious features of neurodegeneration in AT-cerebellar ataxia and dysarthia-are accompanied by a variety of further disabling disease symptoms. Review of the literature outlines a complex pattern of central nervous degeneration in AT that might have been underestimated so far. Neurodegeneration in AT is closely related to the absence or partial lack of the ataxia telangiectasia-mutated (ATM) kinase. ATM is a central player in maintaining cellular homeostasis. Systemic review of the literature reveals a subset of cellular targets hypothesized to count responsible for degeneration in ATM-deficient neurons. Further systematic cliniconeurological, pathoanatomical, and neuroradiological studies are required to understand the structural basis of this neurodegenerative disease. This better understanding has implications for the treatment of AT patients. Second, biochemical and molecular biological studies aimed at deciphering the pathomechanisms of this progressive disorder are necessary for the development of promising future therapies.

Ataxia-telangiectasia (AT) is a rare autosomal recessive disease, affecting neurologic and immune system. Numerous mutations are described in the ATM gene in several populations. However, in Morocco, few data are available concerning this condition. Our main goal is to determine clinical, immunological, and molecular presentation of Moroccan patients with AT. We screened 27 patients, out of 22 unrelated families, for ATM gene mutations. All our patients showed ataxia, ocular telangiectasia, and immunodeficiency, as well as elevated serum alphafetoprotein levels. Mean age at diagnosis was 5.51 years, and consanguinity rate was 81.8 %. Mean age at onset was 2.02 years, and mean time to diagnosis was 3.68 years. We found 14 different mutations in 19 unrelated families, of which 7 were not reported. Our results showed that c.5644C>T mutation was the most common in our series. However, further studies are required to demonstrate a founder effects on ATM gene in Moroccan patients, who showed mutational heterogeneity otherwise. Our data indicate that direct sequencing of coding exons is sufficient for a high detection rate in ATM in Moroccan population.

Ataxia-telangiectasia (A-T) is an autosomal recessive disease characterized by progressive cerebellar ataxia, oculocutaneous telangiectasia, immunodeficiency, a high incidence of lymphoreticular tumors, and an increased sensitivity to chemoradiotherapy-induced DNA damage. The appropriate cancer therapy remains unknown because of high toxicity rates with full-dose conventional protocols. We present a patient with A-T and nephroblastoma, who received an adapted treatment regimen. To our knowledge this is the second report on nephroblastoma in a patient with A-T but the first with confirmed premortem studies. Although the patient tolerated the chemotherapy regimen well, the patient relapsed and died a year after initial diagnosis.

PURPOSE:

Severe combined immunodeficiency (SCID) is characterized by failure of T lymphocyte development and absent or very low T cell receptor excision circles (TRECs), DNA byproducts of T cell maturation. Newborn screening for TRECs to identify SCID is now performed in several states using PCR of DNA from universally collected dried blood spots (DBS). In addition to infants with typical SCID, TREC screening identifies infants with T lymphocytopenia who appear healthy and in whom a SCID diagnosis cannot be confirmed. Deep sequencing was employed to find causes of T lymphocytopenia in such infants.

METHODS:

Whole exome sequencing and analysis were performed in infants and their parents. Upon finding deleterious mutations in the ataxia telangiectasia mutated (ATM) gene, we confirmed the diagnosis of ataxia telangiectasia (AT) in two infants and then tested archival newborn DBS of additional AT patients for TREC copy number.

RESULTS:

Exome sequencing and analysis led to 2 unsuspected gene diagnoses of AT. Of 13 older AT patients for whom newborn DBS had been stored, 7 samples tested positive for SCID under the criteria of California's newborn screening program. AT children with low neonatal TRECs had low CD4 T cell counts subsequently detected (R = 0.64).

CONCLUSIONS:

T lymphocytopenia in newborns can be a feature of AT, as revealed by TREC screening and exome sequencing. Although there is no current cure for the progressive neurological impairment of AT, early detection permits avoidance of infectious complications, while providing information for families regarding reproductive recurrence risks and increased cancer risks in patients and carriers.

Ataxia-telangiectasia (A-T) is a rare neurodegenerative immunodeficiency disorder caused by mutations in the ataxia telangiectasia mutated gene. Patients commonly have lymphopenia and Ig-production abnormalities. We used multicolor flow cytometry and IL-7 ELISA to investigate the effect of A-T and age on the proportions of major lymphocyte subsets and their pattern of CD95 expression in relation to IL-7 levels in 15 classical A-T patients. We also analyzed the sensitivity of T cells from four classical A-T patients to CD95-mediated apoptosis using TUNEL and caspase-activation assays. Our results confirmed lymphopenia and a deficiency in naive T and B cells in A-T patients. In contrast to controls, the proportions of naive and memory T and B cell subsets in A-T patients did not vary in relation to age. There was no evidence of a deficiency in plasma IL-7 or IL-7R expression, and IL-7 concentration correlated positively with CD95 expression on CD4(+) T cells. CD95 expression on unstimulated A-T lymphocytes was high, and the apoptotic sensitivity of activated naive and central memory T cells was increased. These findings show that the immunodeficiency in A-T patients may be described as congenitally aged and is not progressive. The naive cell deficiency is not related to a deficiency in IL-7 or its receptor. However, IL-7 may upregulate CD95 on A-T lymphocytes. High CD95 expression and increased apoptotic sensitivity of activated naive and central memory T cells may result in an increased level of CD95-mediated apoptosis, which could contribute to the congenital lymphopenia in A-T.

Ataxia-telangiectasia is an autosomal recessive disease characterized by progressive cerebellar ataxia, oculocutaneous telangiectasia, immunodeficiency, high incidence of cancer, and increased sensitivity to ionizing radiation. The authors report a case of dysgerminoma in a child with high alpha-fetoprotein, CA125 and beta-human chorionic gonadotropin, who has been followed-up for ataxia-telangiectasia for 2 years.

A gene locus for ataxia-telangiectasia (A-T) is in chromosome region 11q22 to 11q23 and predisposes to cancer. Ataxia-telangiectasiapatients appear to have two separate clinical patterns of malignancy. One pattern involves solid tumors, which have not been stressed and which include malignancies in the oral cavity, breast, stomach, pancreas, ovary, and bladder. Detection of a solid tumor in an A-T patient should serve as a warning. It heralds a markedly elevated risk of another malignancy in that patient. The second pattern of neoplasia in A-T is well recognized and consists of lymphocytic leukemia and non-Hodgkin's lymphoma. These malignancies may relate to immunodeficiency in A-T and to chromosome breakage and rearrangement, which are a feature of A-T. These two patterns of malignancy may be truly separate and reflect different mechanisms of malignancy in A-T, or they may not really be separate but instead reflect a single mechanism of malignancy. The situation in A-T is reminiscent of that in the acquired immunodeficiency syndrome (AIDS), in which Kaposi's sarcoma occurs with mild immunodeficiency and pneumocystis carinii pneumonia occurs with more profound immunodeficiency owing to the human immunodeficiency virus. Next to pulmonary disease, cancer is the leading cause of death in A-T.

The autosomal recessive human disorder ataxia-telangiectasia (A-T) was first described as a separate disease entity 40 years ago. It is a multisystem disease characterized by progressive cerebellar ataxia, oculocutaneous telangiectasia, radiosensitivity, predisposition to lymphoid malignancies and immunodeficiency, with defects in both cellular and humoral immunity. The pleiotropic nature of the clinical and cellular phenotype suggests that the gene product involved is important in maintaining stability of the genome but also plays a more general role in signal transduction. The chromosomal instability and radiosensitivity so characteristic of this disease appear to be related to defective activation of cell cycle checkpoints. Greater insight into the nature of the defect in A-T has been provided by the recent identification, by positional cloning, of the responsible gene, ATM. The ATM gene is related to a family of genes involved in cellular responses to DNA damage and/or cell cycle control. These genes encode large proteins containing a phosphatidylinositol 3-kinase domain, some of which have protein kinase activity. The mutations causing A-T completely inactivate or eliminate the ATM protein. This protein has been detected and localized to different subcellular compartments.

Hematologic malignancies, in particular T-cell lymphomas/leukemias, are prevalent in patients with ataxia telangiectasia (AT), with most reported cases being clinically aggressive and high grade. Epstein-Barr virus (EBV) is often associated with lymphoid proliferations/neoplasms arising in immunodeficient patients. Reports of low-grade B-cell neoplasms in the ataxia telangiectasia population are extremely rare. Here, we describe a case of EBV-associated extranodal marginal zone lymphoma (mucosa-associated lymphoid tissue lymphoma) of the parotid gland in a 16-year-old boy with AT. In addition, we review the literature of hematologic malignancies in the AT population as well as the occurrence of EBV in mucosa-associated lymphoid tissue lymphoma.