Definitive

Male or female patient with either increased radiation induced chromosomal breakage in cultured cells, or progressive cerebellar ataxia, who has disabling mutations on both alleles of ATM.

Probable

Male or female patient with progressive cerebellar ataxia and three out of the following four findings:

1. Ocular or facial telangiectasia
2. Serum IgA less than 2 SD below normal for age
3. Alpha fetoprotein more than 2 SD above normal for age
4. Increased radiation induced chromosomal breakage in cultured cells

Possible

Male or female patient with progressive cerebellar ataxia and at least one of the following four findings:

1. Ocular or facial telangiectasia
2. Serum IgA less than 2 SD below normal for age
3. Alpha fetoprotein more than 2 SD above normal for age
4. Increased chromosomal breakage after exposure to irradiation

Spectrum of disease

AT is a progressive neurologic disorder. Most patients begin to have difficulty walking at the end of the first year of life and are wheelchair bound by the teenage years. Ocular or facial telangiectasia are usually noted at 4-8 years of life. Many patients have recurrent respiratory infections. Leukemia or lymphomas are seen in 10-15% of patients and may be the presenting finding. Some patients are not recognized to have AT until the second decade of life.

Differential diagnosis

Nijmegen breakage syndrome

Further information

• Patient and Family Handbook For The Primary Immune Deficiency Diseases by IDF.
• Diagnosing A-T by the A-T Children's Project.
• Diagnosing A-T by the National Organization to Treat A-T.