Ataxia–telangiectasia (AT) (MIM 208900) is a neurodegenerative disorder whose onset is marked by slowly progressive ataxia that usually begins in early childhood, telangiectasias (dilated small blood vessels), variable immunodeficiency, and cellular sensitivity to ionizing radiation. AT is an autosomal recessive disorder affecting males and females equally, and estimates of the incidence range from 1 in 40 000 to 1 in 100 000 (Haidar et al., 2000; Brown et al., 2000). The gene frequency may be 1% in the general population (Morrell et al., 1986). The most striking non-neurologic feature of AT is an increased frequency of sinopulmonary infections and a dramatically increased risk for malignancy of the lymphoreticular system, especially leukemia and lymphoma.

Clinical features

Skin and scleral findings

The classic skin findings of AT are telangiectasias most prominently involving the sclerae, the earlobes, and the bridge of the nose (Fig. 12.1). Less common sites include the eyelids, the neck, and the antecubital and popliteal fossae. Telangiectasias typically are not present at birth but develop in early childhood, years after the onset of ataxia, usually between the ages of 3 and 6 years with a mean of 72 months (Harding, 1988). Rarely telangiectasias develop in adulthood or not at all and occasionally they disappear later in life.

Two dermatologic features of AT that are sometimes overlooked are hypertrichosis and scattered gray hairs. Hypertrichosis occurs particularly over the forearms. Progeric changes such as poikiloderma, loss of subcutaneous fat, and sclerosis have also been associated with AT.