Ataxia Telangiectasia (AT) is a rare and progressive genetic disorder characterized by primary immunodeficiency and a resultant degradation of the nervous system. The condition manifests itself in childhood, usually within the first decade of life. Initial symptoms include delayed development of motor skills, poor balance and hand co-ordination, chorea, muscle twitches, oculomotor apraxia, and slurred speech. Most children have a weakened immune system, making them susceptible to recurrent infections, most commonly, bronchitis and sinusitis. Telangiectasias, or small, red spider veins, may appear later on the ears, cheeks, or in the corners of the eye. Most children become wheelchair-bound by their teens. Patients have a higher chance of developing cancers, especially acute lymphocytic leukemia or lymphomas.
Mutations in the ATM (Ataxia-Telangiectasia Mutated) gene are responsible for causing AT. Under normal circumstances, this gene codes for a protein kinase that performs two related functions: cell division control and DNA repair in conjunction with the p53 protein. Mutant forms of this gene result in non-functional protein, which cause cellular death, especially in the cerebellum. This leads to the characteristic ataxic symptoms of the condition. In addition, mutant proteins are not able to perform their function of DNA repair, causing defective cells to multiply uncontrollably, resulting in cancers.
