Breaking down the name of A-T...
"Ataxia" refers to poor coordination. The onset of ataxia marks the beginning of progressive degeneration of the cerebellum (a part of the brain) that gradually leads to a general lack of muscle control. Involuntary movements may start at any age and may worsen over time. These extra movements can take many forms, including small jerks of the hands and feet that look like fidgeting (chorea), slower twisting movements of the upper body (athetosis), adoption of stiff and twisted postures (dystonia), occasional uncontrolled jerks (myoclonic jerks), and various rhythmic and non-rhythmic movements with attempts at coordinated action (tremors).
"Telangiectasia" refers to small dilated blood vessels, both of which are hallmarks of the disease (tiny red spider veins). Prominent blood vessels (telangiectasia) over the white (sclera) of the eyes usually occur by the age of 5–8 years, but sometimes later or not at all. The absence of telangiectasia does not exclude the diagnosis of A-T. Although potentially a cosmetic problem, the ocular telangiectasia do not bleed or itch though they are sometimes misdiagnosed as chronic conjunctivitis. It is their constant nature, not changing with time, weather or emotion, which marks them as different from other visible blood vessels. Telangiectasia can also appear on sun-exposed areas of skin, especially the face and ears. They occur in the bladder as a late complication of chemotherapy with cyclophosphamide, have been seen deep inside the brain of older people with A-T, and occasionally arise in the liver and lungs.
Next... How common is A-T?