Ataxia-Telangiectasia in Ophthalmology 

Ataxia-telangiectasia (AT) is a genetic disease characterized by progressive cerebellar ataxia, oculocutaneous telangiectasia, and recurrent respiratory and sinus infections.

The first case described in the literature was a 9-year-old child with progressive cerebellar ataxia and bilateral oculocutaneous telangiectasia reported in 1941 by Madame Louis-Bar. Initially known as the Louis-Bar syndrome, the term ataxia-telangiectasia was introduced in 1958 by Boder et al, who recorded the clinical features and recognized the familial incidence proposing an autosomal recessive mode of inheritance for the disease.^[1] The disease is sometimes referred to as Boder-Sedgwick syndrome.

Progressive cerebellar ataxia usually becomes clinically apparent when the child begins to walk. The ataxia affects station, gait, and intention. Telangiectasia of the bulbar conjunctiva first appears at age 3-7 years and, subsequently, involves the malar areas, palate, ears, and antecubital and popliteal spaces. Other features of this syndrome include retardation of growth, dysarthric speech, dry coarse hair and skin, and mental retardation after age 10 years. The complete syndrome includes hypoplasia of the thymus associated with defective T-cell function and decreased levels of circulating immunoglobulin. Recurrent respiratory tract and sinus infections are common, frequently causing death in adolescence or young adulthood. A high incidence of malignancies, particularly leukemia and Hodgkin's lymphoma, occurs.

Ataxia-telangiectasia combines central nervous system disease with an oculocutaneous anomaly, fulfilling the criteria for classification within the phakomatoses group of diseases.

Ataxia-telangiectasia mainly is due to a defect in a DNA processing or repair protein. The cerebellar and extrapyramidal systems are the most severely affected. This syndrome is characterized by a severe loss of Purkinje cells and, to a lesser degree, the basket and granular cells of the cerebellar cortex. Other pathological changes include cerebellar cortical atrophy, diffuse fibrillary gliosis, and degeneration of the anterior horn cells of the spinal cord. Studies have revealed reduced levels of cerebellar neurotransmitters, including phosphoethanolamine, gamma-aminobutyric acid (GABA), and glutamic acid.

Frequency

United States

The true incidence of ataxia-telangiectasia is unknown. Although ataxia-telangiectasia is rare, the prevalence has been estimated at about 1 in 40,000-50,000.

Mortality/Morbidity

The cause of death in more than 50% of patients with ataxia-telangiectasia is recurrent respiratory infections.

Increased susceptibility to cancer contributes to early mortality in one third to one half of cases. Ataxia-telangiectasia is an autosomal recessive syndrome in which cancers develop in affected homozygotes at a rate approximately 100 times higher than in unaffected age-matched subjects. Retrospective studies have shown that persons heterozygous for the ataxia-telangiectasia gene, who make up about 1% of the general population, also have an excess risk of cancer, particularly breast cancer in women. Patients with ataxia-telangiectasia and cells derived from homozygotes and heterozygotes are unusually sensitive to ionizing radiation.

Sex

Males and females are affected equally.

Age

The mean age of patients with ataxia-telangiectasia at the time of presentation is 2.5-7 years.