(AT) is a rare, inherited childhood neurological disorder that causes degeneration in
the part of the brain that controls motor movements and speech.
AT is caused by a mutation in the gene known as ATM (ataxia-telangiectasia, mutated).
ATM makes a protein that regulates the cell cycle, DNA repair, and cell death. When
this gene is defective, cells are unable to activate the cellular checkpoints that
protect against the damage of ionizing radiation and other agents that can harm DNA.
The disease usually manifests in the first decade of life. Early symptoms include
delayed development of motor skills, poor balance, and slurred speech, usually occurring
during the first decade of life. In most instances, AT has little or no effect on
intellectual development. It affects male and female children with equal frequency.
Ataxic features are progressive and ultimately result in inability to walk. Tiny,
red "spider" veins known as Telangiectasias may develop, appearing in the corners
of the eyes and on the surface of the ears and cheeks. Individuals with AT are acutely
sensitive to ionizing radiation, such as X-rays or gamma-rays.
People with AT are unusually susceptible to developing cancer, most frequently acute
lymphocytic leukemia or lymphoma. Many with AT have a weakened immune system and are
vulnerable to recurrent respiratory infections.