Ataxia teleangiectaticaG11.3

Autosomal recessive, radiosensitive chromosome breakage syndrome with cerebellar ataxia, canities (premature graying), hirsutism, keratosis follicularis, seborrheic eczema, telangiectasias, ephelioid hyperpigmentation, and varioliform atrophies of the face, associated with a T-cellular immunodeficiency and an increased risk of neoplasia (cf.u. Immunodeficiencies, T-cellular, primary).

Genetically heterogeneous, autosomal recessive inherited disease (5 complementation groups known so far). The mutations affect the AT gene located on chromosome 11q22.3 (the mutated gene is called the ATM gene ). The gene locus is in the region of important genes for T cell functions(CD3, THY1, NCAM). The mutations cause disruption of phosphatidylinositol 3-kinase.

Upon detection of double-strand breaks (DSBs), the wild-type kinase encoded by ATM initiates the DNA damage response by phosphorylating histone H2AX and subsequently several other proteins such as BRCA1 (see BRCA1 gene below) and the MRE11-RAD50-NBS1 (MRN) complex, which are placed at the damaged site. In addition, the ATM protein phosphorylates p53, leading to expression of the cyclin-dependent kinase inhibitor p21 and consequent senescence or apoptosis .

The AT gene defect causes, among other things, increased radiosensitivity.

Caution. Iatrogenic tumor induction during extensive radiographic diagnosis. Recombination defect during T cell maturation?

Integument: Canities (premature graying); hirsutism, keratosis follicularis; seborrheic eczema. Teleangiectasias, ephelidal hyperpigmentation(café-au-lait spots), varioliform atrophies of the face.

Neurologic: Progressive cerebellar ataxia, trunk and extremities affected; oculomotor apraxia, typically sloping shoulders, head tilt to one side, generalized muscle weakness, dysarthritic speech, strabismus, nystagmus, peripheral neuropathy, absent tendon reflexes. CT: cerebral atrophy; mental retardation in about one third, usually not marked until 10 years of age.

Immunological: Decreased cellular immune defense (IgA deficiency) leads to decreased resistance to infection with recurrent bacterial infections especially of maxillary sinuses and lungs. Hypoplasia or agenesis of the thymus, hypoplasia of lymphoid tissue.

Pesons with ataxia telangiectasia develop T-cell prolymphocytic leukemia in a clustered manner (former median age between 25-30 years, compared to the "non-Louis Bar collective - Suarez F et al 2015).

Symptomatic, infection prophylaxis with broad-spectrum antibiotic. Genetic counseling!

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