A-T (Ataxia Telangiectasia) is a rare, genetic degenerative disease of childhood, which affects multiple systems of the human body. In people affected with A-T, a gene called ATM is mutated. The ATM gene contains the instructions for the production of the ATM protein. Thus, in A-T patients, the ATM protein is usually not produced at all, or is severely defective. The ATM protein controls many important functions in cells. A major function of ATM is orchestrating the complex response to specific types of damage inflicted on the DNA particularly by ionising radiation. Maintenance of DNA stability and integrity is critical for normal cellular life and therefore, cells devoid of ATM lack this vital defence mechanism. The nervous, immune and reproductive systems are particularly sensitive to the loss of ATM function.
WHAT ARE THE SIGNS AND SYMPTOMS OF A-T?
A diagnosis of A-T comes as a huge shock. There are no indicators at birth and most children with A-T appear ‘seemingly healthy’ in line with their peers during the first year of life. The first signs of A-T are neurological: poor balance and reduced motor coordination (ataxia) being the most prominent, where children are often described as ‘wobbly’. Other signs that follow are deterioration of motor skills, involuntary movements, abnormal eye movements, and difficulty with speech. Further features that may affect some children are insulin-resistant diabetes, premature greying of the hair, difficulty swallowing, drooling and slowed growth. The severity and range of symptoms vary in individual patients.
HOW DOES THE DISEASE PROGRESS?
Research on ‘why’ and ‘how’ the disease progresses continues, as does research into ATM and ATM-related processes. We know that as a child gets older, some types of cells in the central nervous system (CNS) start to die. The patients lose neurons, particularly in a part of the CNS called the “cerebellum”, which controls fine motor coordination. This degeneration in the cerebellum is the prime cause of the progressive neuromotor dysfunction of A-T patients.
HOW DOES A-T AFFECT THOSE DIAGNOSED?
Health progressively deteriorates causing an overall loss of coordination and muscle control. Children are usually confined to a wheelchair by the second decade of life (around the age of 10) and will need assistance with everyday tasks. Children often lose their ability to write, speech becomes slower or slurred and reading becomes problematic due to difficulty in eye movement control. A-T does not affect the mind. There are no learning difficulties linked to having A-T, and affected children and adults are neither intellectually nor socially impaired.
A-T patients are also predisposed to developing cancer (in particular, acute lymphocytic leukemia or lymphoma) and their immune system is weakened. Thus, many of them are susceptible to recurring respiratory infections. A-T is also characterised by telangiectasias (widened, “spider” like veins), which often appear in the corners of the eyes. Due to their inability to respond properly to specific types of DNA lesions, A-T patients also exhibit extreme sensitivity to ionising radiation, such as X-rays.
Life span is shortened, usually by respiratory failure or cancer. A-T is life-limiting, with those affected generally living until their twenties. There is currently no cure for A-T and no treatments to slow down or stop the progression of this devastating disease.