Ataxia-telangiectasia (AT) is an autosomal recessive, multisystem disease causing cerebellar ataxia, mucocutaneous telangiectasias, immunodeficiency, and malignancies. A pilot study reported cognitive and behavioral manifestations characteristic of the cerebellar cognitive affective / Schmahmann syndrome (CCAS). We set out to test and further define these observations because a more comprehensive understanding of the spectrum of impairments in AT is essential for optimal management. Twenty patients (12 males; 9.86 ± 5.5 years, range 4.3 to 23.2) were grouped by age: AT-I (toddlers and preschoolers, n = 7, 4.3-5.9 years), AT-II (school children, n = 7, 5.9-9.8 years), AT-III (adolescents/young adults, n = 6, 12.6-23.2 years). Standard and experimental tests investigated executive, linguistic, visual-spatial, and affective/social-cognitive domains. Results were compared to standard norms and healthy controls. Cognitive changes in AT-I were limited to mild visual-spatial disorganization. Spatial deficits were greater in AT-II, with low average scores on executive function (auditory working memory), expressive language (vocabulary), academic abilities (math, spelling, reading), social cognition (affect recognition from faces), and emotional/psychological processing. Full Scale IQ scores were low average to borderline impaired. AT-III patients had the greatest level of deficits which were evident particularly in spatial skills, executive function (auditory working memory, sequencing, word/color interference, set-shifting, categorization errors, perseveration), academic achievement, social cognition (affect recognition from faces), and behavioral control. Full Scale IQ scores in this group fell in the impaired range, while language was borderline impaired for comprehension, and low average for expression. Cognitive deficits in AT at a young age are mild and limited to visual-spatial functions. More widespread cognitive difficulties emerge with age and disease progression, impacting executive function, spatial skills, affect, and social cognition. Linguistic processing remains mildly affected. Recognition of the CCAS in children with AT may facilitate therapeutic interventions to improve quality of life.

A unique consanguineous family with 2 genomic instability disorders, Fanconi anemia and ataxia telangiectasia, revealed exceptional combinations of null mutations in the FANCA and ATM genes. Two siblings with Fanconi anemia had novel homozygous consecutive microdeletions (c.1361-1370delCCTCCTTTGG, c.1374delC) adjoined to upstream 65 nucleotide direct tandem repeats and deletion hotspot motifs in the FANCA gene. The sibling with ataxia telangiectasia revealed a homozygous p.Arg2993Stop (c.8977C>T) null mutation in the ATM gene. All patients were also heterozygous for the opposite mutations without any additional clinical or laboratory manifestations. Double heterozygote parents did not present any clinical symptoms suggestive of the 2 disorders.

Ataxia-telangiectasia (A-T) is a progressive neurodegenerative disorder with prominent eye movement deficits localizing to the cerebellum. We sought to determine if 4-aminopyridine (4-AP), which putatively enhances the precision of Purkinje neurons, could improve the disorders of eye movements and vestibular function in A-T. The influence of 4-AP on disorders of eye movements and vestibular function was studied in four A-T patients. The effects on the cerebellar control of vestibulo-ocular reflex (VOR) was quantitatively assessed by the decay time constant of per- and post-rotational nystagmus during constant velocity en bloc rotations. The length of the VOR time constant determines the fidelity of the vestibular velocity storage, a neural mechanism that increases the bandwidth of VOR under cerebellar control. The VOR time constant was not increased in A-T patients. The latter is explained by the extent of cerebellar lesion as previously described in A-T and other cerebellar disorders. Nevertheless, 4-AP shortened the VOR time constant during horizontal rotations. Severe disinhibition of velocity storage in subjects with putatively profound cerebellar degeneration manifest periodic alternating nystagmus (PAN). Among two A-T subjects who manifested PAN, 4-AP reduced the peak slow phase velocity of the more severely affected individual and abrogated the PAN in the other. Two A-T subjects manifested horizontal and vertical spontaneous nystagmus (SN) in primary gaze, 4-AP reduced its slow phase velocity. We conclude that in subjects with A-T 4-AP has a prominent effect on the ocular motor and vestibular deficits that are ascribed to the loss of cerebellar Purkinje neurons.

Autosomal recessive ataxia telangiectasia (A-T) is characterized by radiosensitivity, immunodeficiency, and cerebellar neurodegeneration. A-T is caused by inactivating mutations in the ataxia telangiectasiamutated (ATM) gene, a serine-threonine protein kinase involved in DNA damage response and excitatory neurotransmission. The selective vulnerability of cerebellar Purkinje neurons (PN) to A-T is not well understood. Employing global proteomic profiling of cerebrospinal fluid from patients at ages around 15 years, we detected reduced calbindin, reelin, cerebellin-1, cerebellin-3, protocadherin fat 2, sempahorin 7A, and increased apolipoprotein B and J peptides. Bioinformatic enrichment was observed for pathways of lipoproteins, endocytosis, extracellular matrix receptor interaction, peptidase activity, adhesion, calcium binding, and complement immunity. This seemed important since secretion of reelin from glutamatergic afferent axons is crucial for PN lipoprotein receptor endocytosis and lipid signaling. Reelin expression is downregulated by irradiation and reelin/ApoB mutations are known causes of ataxia. Validation efforts in 2-month-old Atm-/- mice before onset of motor deficits confirmed cerebellar transcript reductions for reelin receptors Apoer2/Vldlr with increases for their ligands Apoe/Apoh and cholesterol 24-hydroxylase Cyp46a1. Concomitant dysregulations were found for Vglut2/Sema7a as climbing fiber markers, glutamate receptors like Grin2b, and calcium homeostasis factors (Atp2b2, Calb1, Itpr1), while factors involved in DNA damage, oxidative stress, neuroinflammation, and cell adhesion were normal at this stage. Quantitative immunoblots confirmed ApoB and ApoJ increases and VLDLR reduction in cerebellar tissue at the age of 2 months. These findings show that ApoB excess and reelin signaling deficits reflect the neurodegeneration in A-T in a sensitive and specific way. As extracellular factors, apolipoproteins and their cargo such as vitamin E may be useful for neuroprotective interventions.

Ataxia telangiectasia (A-T) is a rare recessively inherited disorder resulting in a progressive neurological decline. It is caused by biallelic mutation of the ATM gene that encodes a 370 kDa serine/threonine protein kinase responsible for phosphorylating many target proteins. ATM is activated by auto(trans)phosphorylation in response to DNA double strand breaks and leads to the activation of cell cycle checkpoints and either DNA repair or apoptosis as part of the cellular response to DNA damage. The allelic heterogeneity in A-T is striking. While the majority of mutations are truncating, leading to instability and loss of the ATM protein from the allele, a significant proportion of patients carry one of a small number of mutations that are either missense or leaky splice site mutations resulting in retention of some ATM with activity. The allelic heterogeneity in ATM, therefore, results in an equally striking clinical heterogeneity. There is also locus heterogeneity because mutation of the MRE11 gene can cause an obvious A-T like disorder both clinically and also at the cellular level and mutation of the RNF168 gene results in a much milder clinical phenotype, neurologically, with the major clinical feature being an immunological defect.

BACKGROUND:

Ataxia telangiectasia (A-T) is a common inherited cause of early childhood-onset ataxia, distinguished by progressive cerebellum malfunction, capillary vessel extension, and immunodeficiency. The diagnosis of A-T is sometimes difficult to establish in patients with atypical clinical evolution.

CASE REPORT:

We experienced a pediatric 12-years-old female patient, who was finally diagnosed with classic A-T, demonstrating progressive dystonic-myoclonic axial jerks with ataxia as a predominant clinical feature. Oculocutaneous telangiectasias and immune status were unremarkable. Her myoclonic jerks were spontaneous or stimulus-sensitive, and partially ameliorated by levodopa treatment, but the ataxia was slowly progressive. A laboratory examination showed moderate atrophy of the vermis and cerebellum on brain magnetic resonance imaging, elevated serum alpha fetoprotein (AFP) levels, and total absence of A-T mutated (ATM) protein activity. We subsequently confirmed compound heterozygous truncating mutations of the ATM gene in this patient.

CONCLUSION:

Our findings highlight the importance of recognizing dystonic-myoclonic jerks as one of the extrapyramidal signs of classic A-T. Measurement of AFP levels should be considered in patients with unexplained myoclonic jerk movements with ataxia in whom definitive diagnoses are not identified. Physicians should be aware that there are cases where typical findings of A-T may not be fulfilled.

Copyright © 2014 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

A 20-month-old girl diagnosed with T-cell acute lymphoblastic leukemia was treated according to the Nordic NOPHO ALL2000 protocol. The patient developed severe immunosuppression and experienced life-threatening adenovirus infection, which was treated with ribavirin and cidofovir. α-fetoprotein was 20- to 30-fold elevated, and genetic analysis confirmed the diagnosis of ataxia telangiectasia. Despite receiving only 7 weeks of anti-leukemic therapy, she has stayed in first remission now 8 years after the diagnosis. We speculate that this could be because of increased chemosensitivity of ATM-mutated leukemic cells, adenovirus causing a direct oncolytic effect, and/or high levels of endogenous cortisol during her severe infection.

Ataxia telangiectasia (AT) is a rare primary immunodeficiency disorder with various clinical manifestations. Increased serum levels of IgM and recurrent infections, mainly sinopulmonary infections, can be the presenting feature in a number of AT patients and may be initially misdiagnosed as hyper-IgM (HIgM) syndrome. This study was designed to investigate class switch recombination (CSR) as a critical mechanism in B lymphocytes' maturation to produce different isotypes of antibody in response to antigen stimulation in AT cases with HIgM presentation. Quantitative IgE production after stimulation by IL-4 and CD40L was considered as an indicator for CSR function. We also compared their results with sex and age matched AT patients without HIgM presentation. We report four AT patients with recurrent infections during infancy and high serum levels of IgM. Laboratory evaluations revealed defective CSR while none of the three AT patients without HIgM presentation had a defect in the CSR process. The characterized defect in AT is a mutation in the ataxia telangiectasia mutated (ATM) gene. This gene may result in CSR defects due to impaired DNA break repair. A special association between AT and HIgM may indicate a new subgroup of AT patients according to their clinical phenotype and CSR condition.

BACKGROUND:

Ataxia telangiectasia (A-T) is a genetic disorder caused by the homozygous mutation of the A-T mutated gene. It is frequently associated with variable degrees of cellular and humoral immunodeficiency. However, the immune defects in A-T patients are not well characterized. To the best of our knowledge, no studies have focused on the major lymphocyte subpopulations and recent thymic emigrants of A-T patients in comparison with age-matched healthy controls.

METHODS:

Following the European Society for Immunodeficiencies criteria, 17 patients diagnosed with A-The, and 12 age-matched healthy children were assigned to the study. Both patients and healthy controls were grouped as 1-5, 6-10, 11-15, and 15+ years. By using a flow cytometer, major lymphocyte subpopulations and CD4+CD45RA+CD31+ recent thymic emigrants were determined as percentage and absolute cell numbers and compared.

RESULTS:

No significant differences in all lymphocyte subpopulations were observed between the age groups of A-T patients. Compared to the healthy controls, there was a decrease in T cells, effector memory T4 cells, B cells, naïve B cells, naïve T4 cells, switched B cells, and recent thymic emigrants and an increase in active T8 cells and non-switched B cells in the percentage and absolute number of some cell populations in the A-T group.

CONCLUSIONS:

This study showed that effector functions in some cell lymphocyte populations were decreased in A-T patients.

Copyright © 2014 SEICAP. Published by Elsevier Espana. All rights reserved.

Magnetic resonance imaging (MRI) research in identifying altered brain structure and function in ataxia-telangiectasia, an autosomal recessive neurodegenerative disorder, is limited. Diffusion-weighted MRI were obtained from 11 ataxia telangiectasia patients (age range, 7-22 years; mean, 12 years) and 11 typically developing age-matched participants (age range, 8-23 years; mean, 13 years). Gray matter volume alterations in patients were compared with those of healthy controls using voxel-based morphometry, whereas tract-based spatial statistics was employed to elucidate white matter microstructure differences between groups. White matter microstructure was probed using quantitative fractional anisotropy and mean diffusivity measures. Reduced gray matter volume in both cerebellar hemispheres and in the precentral-postcentral gyrus in the left cerebral hemisphere was observed in ataxia telangiectasia patients compared with controls (P < 0.05, corrected for multiple comparisons). A significant reduction in fractional anisotropy in the cerebellar hemispheres, anterior/posterior horns of the medulla, cerebral peduncles, and internal capsule white matter, particularly in the left posterior limb of the internal capsule and corona radiata in the left cerebral hemisphere, was observed in patients compared with controls (P < 0.05). Mean diffusivity differences were observed within the left cerebellar hemisphere and the white matter of the superior lobule of the right cerebellar hemisphere (P < 0.05). Cerebellum-localized gray matter changes are seen in young ataxia telangiectasia patients along with white matter tract degeneration projecting from the cerebellum into corticomotor regions. The lack of cortical involvement may reflect early-stage white matter motor pathway degeneration within young patients.

Since identification of mutations in the ATM gene leading to ataxia-telangiectasia, enormous efforts have been devoted to discovering the roles this protein plays in DNA repair as well as other cellular functions. Even before the identification of ATM mutations, it was clear that other diseases with different genomic loci had very similar neurological symptoms. There has been significant progress in understanding why cancer and immunodeficiency occur in ataxia-telangiectasia even though many details remain to be determined, but the field is no closer to determining why the nervous system requires ATM and other DNA repair genes. Even though rodent disease models have similar DNA repair abnormalities as the human diseases, they have no consistent, robust neuropathological phenotype making it difficult to understand the neurological underpinnings of disease. Therefore, it may be useful to reassess the neurological and neuropathological characteristics of ataxia-telangiectasia in human patients to look for potential commonalities in DNA repair diseases that result in ataxia. In doing so, it is clear that ataxia-telangiectasia and similar diseases share neurological features other than merely ataxia, such as length-dependent motor and sensory neuropathies, and that the neuroanatomical localization for these symptoms is understood. Cells affected in ataxia-telangiectasiaand similar diseases are some of the largest single nucleated cells in the body. In addition, a subset of these diseases also has extrapyramidal movements and oculomotor apraxia. These neurological and neuropathological similarities may indicate a common DNA repair related pathogenesis with very large cell size as a critical risk factor.

BACKGROUND:

Pediatric cerebrocerebellar neurodegenerative disorders such as ataxia-telangiectasia (AT) have not been examined in detail for neuropsychologic changes. Such studies may contribute to the further understanding of ataxia-telangiectasia and to the role of the cerebrocerebellar system in the development of cognitive function in childhood.

METHODS:

Twenty-two patients with the classic phenotype of ataxia-telangiectasia were grouped into early stage cerebellar disease (group AT-I) versus late stage cerebrocerebellar disease (group AT-II) and examined for neurocognitive features. Results were compared with those of healthy control subjects and with standard norms.

RESULTS:

Patients in AT-I group scored low average compared with standard norms on all tests and were impaired compared with healthy control subjects for verbal intelligence quotient (P < 0.001), vocabulary and comprehension (P = 0.007), processing speed (P = 0.005), visuospatial processing (P = 0.020), and working memory (P = 0.046). Patients in AT-II group scored below average compared with standard norms on all tests and were impaired compared with control subjects for attention (P < 0.001), working memory (P < 0.001), and abstract reasoning (P < 0.001). Comprehension scores were lower for patients in AT-II than in AT-I group (P = 0.002), whereas vocabulary scores showed no difference between groups (P = 0.480).

CONCLUSION:

Cognitive impairments in ataxia-telangiectasia present early, coinciding with cerebellar pathology and are characteristic of the cerebellar cognitive affective syndrome. Widespread and deeper cognitive deficits manifest in later stages of ataxia-telangiectasia when additional noncerebellar pathology develops. These results are the first indications of distinct cerebellar and extracerebellar and/or subcortical contributions to the range of cognitive domains affected in ataxia-telangiectasia and need to be confirmed in future studies.

Copyright © 2014 Elsevier Inc. All rights reserved.

OBJECTIVE:

Ataxia telangiectasia (AT) is a rare genetic, multi-system disorder characterized by neurodegeneration, chromosome instability, B and T cell immunodeficiency and a predisposition to cancer. We examined immunologic parameters reflecting cell development and proliferation and their relevancy to the clinical phenotype in affected individuals.

PATIENTS AND METHODS:

AT patients from the AT National Clinic in Israel underwent immunological investigation. Their T and B cell workup included lymphocyte subset counts, immunoglobulin levels, responses to mitogenic stimulations, TCR-Vβ families and BCR immunoglobulin heavy chain spectratyping, TCR rearrangement excision circles (TRECs) and Kappa-deleting recombination excision circles (KRECs).

RESULTS:

Thirty-seven AT patients (median age 12.7 years, range 4.2-25.1) were evaluated. CD20 B and CD3 T lymphocytes were decreased in 67 % and 64 % of the patients, respectively, while only 33 % of the patients had reduced lymphoproliferative responses. Almost all AT patients displayed extremely low TRECs and KRECs levels, irrespective of their age. Those levels were correlated to one another and to the amounts of CD3+ and CD20+ cells, respectively. Abnormal TCR-Vβ repertoires were found with different degrees of clonality or reduced expression in these AT patients. There was no clear clustering of expansions to specific TCR-Vβ genes. PCR spectratyping analysis of the FR2 IgH BCR gene rearrangements in peripheral blood was abnormal in 50 % of the patients.

CONCLUSION:

The immunodeficiency associated with AT is combined, remains low over time and not progressive. It is characterized by low TREC and KREC copies suggestive of abnormal T and B cell neogenesis.

Ataxia-telangiectasia-like disorder (ATLD) is a rare autosomal recessive disorder, and has symptoms similar to ataxia-telangiectasia (AT). ATLD is caused by mutations in the MRE11 gene, involved in DNA double-strand break repair (DSBR). In contrast to AT, ATLD patients lack key clinical features, such as telangiectasia or immunodeficiency, and are therefore difficult to be diagnosed. We report a female ATLD patient presenting with hypergonadotropic hypogonadism and hypersegmented neutrophils, previously undescribed features in this disorder, and potential diagnostic clues to differentiate ATLD from other conditions. The patient showed slowly progressive cerebellar ataxia from 2 years of age, and MRI revealed atrophy of the cerebellum, oculomotor apraxia, mild cognitive impairment, writing dystonia, hypergonadotropic hypogonadism with primary amenorrhea, and hypersegmented neutrophils. Western blot assay demonstrated total loss of MRE11 and reduction of ATM-dependent phosphorylation; thus, we diagnosed ATLD. Genetically, a novel missense mutation (c.140C>T) was detected in the MRE11 gene, but no other mutation was found in the patient. Our presenting patient suggests that impaired DSBR may be associated with hypergonadotropic hypogonadism and neutrophil hypersegmentation. In conclusion, when assessing patients with ataxia of unknown cause, ATLD should be considered, and the gonadal state and peripheral blood smear samples evaluated.

A number of diseases exhibit neurodegeneration with/without additional symptoms such as immunodeficiency, increased cancer risk, and microcephalus. Ataxia telangiectasia and Nijmegen breakage syndrome, for example, develop as a result of mutations in genes involved in the DNA damage response. However, such diseases can be difficult to diagnose as they are only rarely encountered by physicians. To overcome this challenge, nine patients with symptoms that resemble those of ataxia telangiectasia, including neurodegeneration, hypogammaglobulinemia, telangiectasia, and/or elevated serum α-fetoprotein, were subjected to whole-exome sequencing (WES) to identify the causative mutations. Molecular diagnosis was achieved in two patients: one displayed CD40 ligand (CD40LG) deficiency, while a second showed a homozygous SIL1 mutation, which has been linked to Marinesco-Sjögren syndrome (MSS). Typical features of CD40LG deficiency and MSS are distinct from the symptoms usually seen in ataxia telangiectasia. These dissociations between phenotype and genotype make it difficult to achieve molecular diagnosis of orphan diseases. Whole-exome sequencing analyses will assist in the molecular diagnosis of such cases and allow the identification of genotypes that would not be expected from the phenotype.

Inactivation of the Ataxia Telangiectasia Mutated gene in chronic lymphocytic leukemia results in resistance to p53-dependent apoptosis and inferior responses to treatment with DNA damaging agents. Hence, p53-independent strategies are required to target Ataxia TelangiectasiaMutated-deficient chronic lymphocytic leukemia. As Ataxia Telangiectasia Mutated has been implicated in redox homeostasis, we investigated the effect of the Ataxia Telangiectasia Mutated-null chronic lymphocytic leukemia genotype on cellular responses to oxidative stress with a view to therapeutic targeting. We found that in comparison to Ataxia Telangiectasia Mutated-wild type chronic lymphocytic leukemia, pro-oxidant treatment of Ataxia Telangiectasia Mutated-null cells led to reduced binding of NF-E2 p45-related factor-2 to antioxidant response elements and thus decreased expression of target genes. Furthermore, Ataxia Telangiectasia Mutated-null chronic lymphocytic leukemia cells contained lower levels of antioxidants and elevated mitochondrial reactive oxygen species. Consequently, Ataxia Telangiectasia Mutated-null chronic lymphocytic leukemia, but not tumors with 11q deletion or TP53 mutations, exhibited differentially increased sensitivity to pro-oxidants both in vitro and in vivo. We found that cell death was mediated by a p53- and caspase-independent mechanism associated with apoptosis inducing factor activity. Together, these data suggest that defective redox-homeostasis represents an attractive therapeutic target for Ataxia Telangiectasia Mutated-null chronic lymphocytic leukemia.