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Novel genetic variants identification and immune profiling in ataxia telangiectasia patients.

BACKGROUND: Ataxia telangiectasia (AT) is an autosomal recessive neurodegenerative disease. While heterozygous relatives of AT patients are known to be clinically healthy, a predisposition to various pathologies has been reported. Our aim was firstly, to further characterize the clinical features and broaden the spectrum of genetic pathogenic variants in AT patients. Secondly, we aimed to study the immune profiles of AT patients and their relatives to identify similarities or common biomarkers. METHODS: A Target Gene Sequencing for six patients suspected with AT was performed. Computational analysis was conducted to assess the pathogenicity of novel variants. The distribution of immune cells was assessed by flow cytometry in patients with AT, AT-like disorder, Friedreich ataxia, and in AT relatives. The expression pattern of candidate genes was evaluated by RT-qPCR. RESULTS: We identified and predicted the pathogenicity of novel variants in the ATM gene. Computational analysis suggested that the novel identified missense mutation could affect ATP binding pattern and ATM protein flexibility, while Alu element insertion could probably induces a premature stop codon. Furthermore, our results confirm the pathogenic effect of identified splicing mutations on the ATM transcript. Moreover, we noticed a high percentage of LTCD4 + and LTCD8 + senescent subsets in AT patients and a relative increase of the of intermediate and non-classical monocytes accompanied with a decrease of classical monocytes specifically in AT patients with truncated biallelic mutations which was intriguingly similar to the immune profile of AT parents. In addition, a difference of immune pattern was observed between AT patients with biallelic truncated mutations compared to those with at least one non-truncated mutation, with a variability intragroup. Gene expression analysis identified FOXO3, IL33 and METTL3 as putative genes that may yield clues into AT pathogenesis. CONCLUSION: Taken together, our study expands the mutational spectrum of AT disease worldwide and further characterize the immune profile of AT patients uncovering a possible difference in some immune cellular subsets related to ATM mutation type and delineate putative immune abnormalities related to ATM heterozygosity among AT parents. Furthermore, dysregulation in FOXO3, IL33 and METTL3 expression could be related to disease severity.

Humans

Ataxia-telangiectasia and hepatocellular carcinoma.

Ataxia-telangiectasia (AT) is a multi-system disease involving the cerebellum, cutaneous blood vessels and the immune system including both cellular and humoral components. It also involves hematological, endocrine and peripheral nervous systems. This disease is often associated with abnormal liver function tests, such as, raised alkaline phosphatase and various nonspecific histological changes in the liver. High incidence of various malignancies involving lymphoreticular, gastrointestinal and mesenchymal organs have reported in ataxia-telangiectasia. Elevated levels of alpha fetoprotein have been noted commonly in this disorder. In spite of the hepatic histological and biochemical changes associated with elevated alpha fetoprotein, to our knowledge, development of hepatocellular carcinoma has not been reported in patients with ataxia-telangiectasia. A case of a young white female with AT who developed hepatocellular carcinoma along with significantly elevated levels of alpha fetoprotein is presented.

Adult

[Ataxia telangiectasia (Louis-Bar syndrome)].

Ataxia telangiectasia (Louis-Bar syndrome) represents a disease of childhood, characterized by diffuse telangiectasia of the skin and the conjunctivae and cerebellar ataxia. Patients are frequently predisposed for infections due to disturbances of the cellular and humoral immunity. This paper discusses the syndrome referring to an own observation of ataxia telangiectasia and literature of the past.

Ataxia Telangiectasia

Neurological effects of encapsulated dexamethasone sodium phosphate in children aged 6-9 years with ataxia telangiectasia (NEAT): a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial.

BACKGROUND: Ataxia telangiectasia is a rare, multisystem disorder with progressive cerebellar neurodegeneration and no approved treatments. The efficacy of corticosteroids, including erythrocyte encapsulated dexamethasone sodium phosphate (eDSP), which have been studied for two decades in this disease, has not yet been proven in randomised trials. We aimed to investigate the safety and efficacy of eDSP in children aged 6-9 years with ataxia telangiectasia. METHODS: NEAT was a multicentre, randomised, double-blind, placebo-controlled phase 3 study, conducted at 20 sites across nine countries (Denmark, Germany, Italy, Norway, Poland, Spain, Switzerland, UK, and USA). Eligible participants were children aged 6 years or older weighing at least 15 kg, with a genetic diagnosis of ataxia telangiectasia and presence of neurological symptoms. Participants were randomly assigned (1:1) to the eDSP or placebo group via an independent interactive web response system and were stratified by age (6-9 years or ≥10 years), sex, and region (USA vs other countries). All participants, investigators, sponsors, and raters were masked to treatment assignments. eDSP was given intravenously every 21-30 days for six doses. All randomly assigned participants were included in the intention-to-treat (ITT) and safety populations; the primary and secondary efficacy analyses were conducted in participants aged 6-9 years in the ITT population. The primary efficacy endpoint was the change in Rescored Modified International Cooperative Ataxia Rating Scale (RmICARS) score between baseline and month 6, and a mixed-model-repeated-measures analysis was used. The trial was registered at ClinicalTrials.gov, NCT06193200, and is completed. FINDINGS: Between June 24, 2024, and Dec 17, 2025, we screened 125 participants for eligibility, of whom 105 (84%) were randomly assigned to the eDSP group (n=51 [49%]) or the placebo group (n=54 [51%]) and received at least one dose of treatment. The mean age was 8·5 years (SD 1·9) in the eDSP group and 8·6 years (2·3) in the placebo group (overall age range 6-17 years). In the eDSP group, 24 (47%) of 51 participants were girls and 27 (53%) were boys and, in the placebo group, 26 (48%) of 54 were girls and 28 (52%) were boys. Of ITT participants aged 6-9 years, 38 (95%) of 40 in the eDSP group and 41 (95%) of 43 in the placebo group completed the study. Compared with the placebo group, no significant differences were identified in change in RmICARS score from baseline to 6 months in participants aged 6-9 years: least squares mean difference -1·30 (95% CI -2·77 to 0·18; p=0·085). Adverse events were reported in 47 (92%) of 51 participants in the eDSP group and in 50 (93%) of 54 participants in the placebo group. The most common treatment-emergent adverse events were vomiting, pyrexia, pruritus, nasopharyngitis, cough, headache, and fatigue. There were no reports of treatment-related serious adverse events or deaths. Safety laboratory parameters did not identify adverse effects on growth, metabolism, bone mineral density, or endocrine function in any of the treatment groups. INTERPRETATION: The primary efficacy endpoint was not achieved, because the effect of eDSP on neurological symptoms did not reach statistical significance. The favourable safety profile of eDSP, previously described in a large study of children with ataxia telangiectasia, was confirmed in this trial. The eDSP programme, comprising two randomised studies and treating the largest cohort of patients with ataxia telangiectasia to date, underscores the need for rigorously designed trials of sufficient duration to detect sustained clinical benefit. FUNDING: Quince Therapeutics.

Humans

Diagnostic considerations in ataxia-telangiectasia.

13 children with ataxia-telangiectasia were followed for 6 years. Unlike previously reported cases, these patients had progressive, debilitating neurological disease and slight pulmonary or infectious symptoms. Immunological dysfunction was variable and endocrinological defects were absent. Oculomotor findings, alpha-fetoprotein levels, and the incidence of chromosomal breakage were the most consistent parameters in the diagnosis of the condition. This disease should be considered in any patient with chronic ataxia, regardless of immunological findings or whether he has a history of infections.

Ataxia Telangiectasia

Endonucleolytic activity for gamma-irradiated DNA in normal and ataxia telangiectasia fibroblast cell extracts.

The increased sensitivity of ataxia telangiectasia cells towards ionizing radiation may be related to their inability to incise DNA near sites of radiation-induced base damages. When compared to 3 unaffected controls, crude extracts from 5 lines of fibroblast cells derived from ataxia telangiectasia patients were capable of incising gamma-irradiated DNA to the same extent as normal cells as determined in a nicking assay, using the circular replicative form of phiX174. However, the types of alterations introduced into DNA by gamma-irradiation could be distinguished from sites of base loss due to depurination or depyrimidination and from sites of base modification by OsO4. The specific endonuclease involved was demonstrated to be distinct from the apurinic endonuclease by its rate of temperature inactivation.

Ataxia Telangiectasia

Eye movements in ataxia-telangiectasia.

The spectrum of eye movement disorders in six patients with ataxia-telangiectasia at different stages of progression was assessed quantitatively by electrooculography. All patients demonstrated abnormalities of voluntary and involuntary saccades. The youngest and least involved patient had significantly increased reaction times of voluntary saccades, but normal accuracy and velocity. The other patients demonstrated increased reaction times and marked hypometria of horizontal and vertical voluntary saccades. Saccade velocity remained normal. Vestibular and optokinetic fast components (involuntary saccades) had normal amplitude and velocity but the eyes deviated tonically in the direction of the slow component. We conclude that patients with ataxia-telangiectasia have a defect in the initiation of voluntary and involuntary saccades in the earliest stages. These findings are distinctly different from those in other familial cerebellar atrophy syndromes.

Adolescent

Gastric adenocarcinoma due to ataxia-telangiectasia (Louis-Bar syndrome).

A 26-year-old male with ataxia-telangiectasia died with a gastric adenocarcinoma. Malignancy is a recognised complication of this condition, the majority of cases being reticuloendothelial. There have been three reports of gastric adenocarcinoma associated with ataxia-telangiectasia; this, however, is the first in British published reports.

Adenocarcinoma

Gonadal dysfunction in patients with ataxia telangiectasia.

Two males and three females with ataxia telangiectasia aged from 4 6/12 to 23 years were subjected to an i.v. LH-RH test. All were found to have elevated basal levels of FSH and three had elevated levels of LH. In all the response of FSH to LH-RH was supranormal. In the pubertal and adult females the basal levels of estradiol were low. The laboratory and clinical findings in these patients as well as data reported by others indicated that the primary gonadal failure is an integral part of AT.

Adolescent

The response of ataxia telangiectasia cells to bleomycin.

The autosomal recessive disorder, ataxia telangiectasia (AT) is characterised by cellular sensitivity to ionizing radiation. The molecular basis of this radiosensitivity is the subject of controversy. We report here that cultured fibroblasts from AT patients are also sensitive to the lethal effects of bleomycin. As with ionizing radiation, no defect has been observed in the overall rejoining of single or double-strand breaks produced by bleomycin. Since, however, only apyrimidinic (and to a lesser extent apurinic) sites and strand breaks are known to be produced by bleomycin, we tentatively suggest that AT cells are unable to rejoin a very small fraction of the total strand breaks. We attribute our inability to detect such unrejoined strand breaks to the relative insensitivity of the sucrose gradient procedures normally used to detect strand breaks.

Ataxia Telangiectasia

Selective defects in T cell function in ataxia-telangiectasia.

We have studied three patients with ataxia-telangiectasia (AT) and found two of them to have a normal mixed leucocyte culture stimulating and responding ability. However, all three patients and one parent had defective cell-mediated lympholysis (CML), even in the face of a potent proliferative response to allogeneic leucocytes. None of these patients showed significant proliferative responses to common microbial antigens (tetanus toxoid, Candida albicans, purified protein derivative (PPD), diphtheria toxoid, influenza). Our studies indicate tha the T cell defect in AT preferentially affects certain T cell functions associated with antigen recognition and the generation of allogeneic CML, while sparing the allogeneic proliferative response. The selective deficiency of specific lymphocyte functions in a thymic immunodeficiency with a known defect in DNA repair is consistent with the concept that DNA modulating enzymes are important for T cell function.

Antigens

Exploiting the weak link: Ataxia-Telangiectasia Mutated dysfunction in oesophagogastric tumours.

ATM (ataxia-telangiectasia mutated) is a central regulator of the DNA damage response, coordinating double-strand break repair, checkpoint control, and cell fate decisions. Its disruption drives genomic instability and has been implicated across multiple tumour types. In oesophagogastric cancers, ATM alterations occur in a clinically relevant subset of cases, encompassing both somatic and germline events, and are associated with distinct molecular features including reduced co-occurrence with TP53 mutations and elevated homologous recombination deficiency scores. This narrative review synthesises published literature and publicly available genomic databases to examine ATM biology, the spectrum of ATM alterations across oesophageal adenocarcinoma, oesophageal squamous cell carcinoma, and gastric cancer subtypes, and the challenges of defining true ATM deficiency. The therapeutic implications of ATM dysfunction are evaluated across radiotherapy, platinum-based chemotherapy, ATR inhibition, and PARP inhibition. ATM alterations are detected in approximately 6% of tumours pan-cancer and in up to 10% of oesophagogastric cases. Defining ATM deficiency remains challenging, as immunohistochemistry, next-generation sequencing, and functional assays each carry distinct limitations. ATR inhibition emerges as the most consistently supported therapeutic strategy, with converging preclinical and early clinical evidence across oesophagogastric models. By contrast, available data do not support treating ATM deficiency as equivalent to BRCA-like homologous recombination deficiency, and PARP inhibitor monotherapy has not demonstrated consistent benefit. Prospective validation of functional ATM assays, histology-stratified trial design, and integration of genomic, protein-level, and functional evidence represent key priorities for translating ATM-guided strategies into oesophagogastric cancer practice.

Humans

Effect of thymic humoral factor on cellular immune factors of normal children and of pediatric patients with ataxia telangiectasia and Down's syndrome.

Cellular immune functions of nine Down's syndrome patients and of nine was Ataxia telangiectasia vs. nine normal children and nine cord bloods, were evaluated using in vitro assays of peripheral blood lymphocytes. The in vitro assays included E rosette formation, antilymphocytic cytotoxicity by an antithymic antiserum and leukocyte migration inhibition factor (LIF) production. The mitogens and antigens used were phytohemagglutinin, purified protein derivative, and monilia antigen. The effect of a thymic hormone (THF) on these parameters was evaluated and it was administered therapeutically to three Down's syndrome patients and to two patients with Ataxia telangiectasia. Most deficient T-cell functions were reversed to normal after incubation of the lymphocytes with THF, or after THF therapeutic administration. In two Down's syndrome cases, the clinical course was not altered by THF administration, while one seemed to benefit from it markedly. One of the Atactic patients recovered from a severe viral infection, while the other died from intractable bronchopneumonia.

Ataxia Telangiectasia

Ataxia-telangiectasia with a 32 year survival. A clinicopathological report.

The clinicalpathological findings in a 32-year old woman with ataxia-telangiectasia are presented. This is the oldest patient with this disease to be studied thoroughly clinically and at autopsy. Multiple small gliovascular malformations in the brain and spinal cord and telangiectasis of the liver were found. Other advanced lesions of ataxia-telangiectasia are illustrated. The vascular malformations of the central nervous system and liver are unique. The patient died of a malignant lymphoproliferative disorder and had five other malignant and benign neoplasms.

Adult

Apurinic and/or apyrimidinic endonuclease activity in ataxia telangiectasia cell extracts.

The possibility that the increased sensitivity of ataxia telangiectasia towards ionizing radiation is related to a DNA-repair deficiency has been examined further. When compared to unaffected controls, 6 lines of fibroblast cells derived from ataxia patients demonstrated a slightly reduced endonucleolytic activity (165 +/- 12 units vs. 214 +/- 28 units) towards apurinic and/or apyrimidinic sites as determined in a "nicking" assay.

Acid Phosphatase

Unusual sensitivity of ataxia telangiectasia cells to bleomycin.

Peripheral blood lymphocytes from four patients with ataxia telangiectasia (AT), an inherited disorder showing, among other features, radiosensitivity and a high frequency of cancers, were shown to be cytogenetically more sensitive to bleomycin than were lymphocytes from both normal individuals and a single patient with xeroderma pigmentosum. With cell survival techniques, a biphasic dose-response curve was seen for both normal and AT fibroblasts, although the AT cells showed a much lower survival. The increased sensitivity to bleomycin in AT cells might be expected since it is a radiomimetic drug, but more importantly the known action of bleomycin in producing DNA strand scission suggests that AT cells might be defective in rejoining a proportion of DNA strand breaks.

Ataxia Telangiectasia

[Ataxia telangiectasia (Louis-Bar syndrome)].

The Authors relate on a case of ataxia-telangiectasia, where appeared all the signs of this peculiar disease of the childhood. Finally they discuss on literature and pathogenesis.

Ataxia Telangiectasia

Transfer factor therapy in ataxia--telangiectasia.

The effects of weekly doses of transfer factor in four patients with ataxia--telangiectasia were investigated following a total course of 2 months therapy. Transfer factor administration showed no influence on the absolute lymphocyte counts, T-cell rosettes or antibody titres to EBV, but it caused conversion of skin-test reactivity and production of MIF to various antigens. There was a dissociation in blastic transformation response, the skin-test responses and MIF production. Serum interferon levels were low before, and 2, 6 and 24 hr after, therapy. Clinically no improvement in infections was observed following transfer factor therapy.

Antibodies, Viral