The first presenting symptom of A-T is generally ataxia. Children with A-T usually have a delayed onset of walking and when they do, they sway, stagger and wobble. They are usually unstable when sitting unsupported or when trying to stand in one place (for example, when standing in front of a sink to brush their hair or teeth). The ataxia is caused by abnormalities in the cerebellum, a part of the brain that controls balance and movement. As toddlers, most children with A-T are thought to have a neurologic disorder such as cerebral palsy or an unspecified movement disorder. The diagnosis of A-T is often difficult to make when ataxia is the only symptom present.
A-T causes progressive decline of motor neurologic function, which may not be apparent until age 4 or 5 years. It is the deterioration that most often leads to the correct diagnosis, as neurologic deterioration does not happen to people with cerebral palsy. With increasing age, children with A-T develop abnormalities in eye movements (delayed initiation of eye movement, jerky eye movements and difficulty with eye/head coordination when tracking moving objects or following a single line of print in a book), and fine motor control (writing or feeding themselves). They have more and more difficulty walking and usually need to use a wheelchair for at least part of the day by the age of 10-12 years. They develop an intention tremor, and difficulties with speaking (dysarthria) and swallowing (dysphagia). While the neurologic symptoms progress in all children, the rate of progression and the relative severity of each neurologic problem vary widely from individual to individual.
Dilated and corkscrew-shaped blood vessels (telangiectasias) cause the whites of the eyes to look bloodshot or as if there is pink eye (conjunctivitis) or an allergy. Telangiectasias eventually occur in most patients with A-T but do not occur in all patients with A-T and are only rarely present in infants and very young children, another reason that the diagnosis of A-T may be delayed until school age. Telangiectasias may also be seen on sun-exposed areas of skin such as the ears, neck and extremities.
Patients with A-T have an increased susceptibility to infection. Infections most commonly affect the lungs and/or sinuses and can be caused by bacteria and viruses. Part of the explanation for these infections is immunodeficiency, particularly related to low immunoglobulin levels and problems making antibody. About two thirds of people with A-T have low levels or complete deficiency of IgA, the antibody that protects us from infections on mucosal surfaces (such as the inside of the cheek and lining of the airways, nose and intestines). Many patients have problems making antibody responses to vaccines and infections. There is a particular problem making antibody to the large sugar molecules (polysaccharides) found on the outside of some of the bacteria that are frequent causes of sinusitis, bronchitis and pneumonia. These deficient antibody responses may be associated with low levels of IgG, IgA, IgM and/or IgG subclasses.
The immunodeficiency of A-T generally remains stable over time but gets worse with age in about 15% of patients. A thorough evaluation by an immunologist is necessary for every patient with A-T to determine if there is a deficiency of humoral immunity that is severe enough to require immunoglobulin replacement or other therapy. The usual indication for immunoglobulin is a problem making antibody, not just a low level of one or more immunoglobulin classes.
Most patients with A-T have reduced numbers of T- and B-lymphocytes, an abnormality that can be easily measured by a blood test. They may have problems with warts and a skin infection called molluscum, but they do not usually get opportunistic infections. However, if they are treated with steroids (such as prednisone) at high doses or for long periods of time, or if they need chemotherapy to treat cancer, the T-lymphocyte counts may become low enough that they become susceptible to opportunistic infections such as pneumocystis pneumonia.
Immunodeficiency is not the only explanation for lung infections in patients with A-T. Problems with swallowing (dysphagia) can cause aspiration. This occurs when solid foods or liquids go down the windpipe (trachea) and into the lungs instead of going down the esophagus into the stomach. Patients with A-T also have an ineffective cough, so they have difficulty clearing aspirated material and mucus from the airways. Chronic lung infections are sometimes managed by using prophylactic (preventive) antibiotics, and wearing special vibrating vests several times a day to help clear mucus. A gastrostomy tube may be inserted to provide calories directly into the stomach, providing nutrition and decreasing the amount of food and liquid that needs to be taken by mouth.
Patients with A-T are at an increased risk for developing all types of cancers, but particularly cancers of the immune system (lymphomas or leukemias). Cancer occurs in about 1/4 of all patients with A-T. It can occur at any age, and the risk cannot be predicted by the severity of immunodeficiency or any other feature of the disease.