Male or female patient with either increased radiation induced chromosomal breakage in cultured cells or microcephaly, who has NBS-1, the gene defective located on chromosome 8q21 on both alleles.

Male or female patient with three out of the following five findings:

1. microcephaly
2. typical facial appearance
3. lymphoma, leukemia
4. serum IgG and IgA more than 2 SD below normal for age
5. increased radiation induced chromosomal breakage in cultured cells

Male or female patient with at least one of the following five findings:

1. microcephaly
2. typical facial appearance
3. lymphoma, leukaemia
4. serum IgG and IgA more than 2 SD below normal for age
5. Increased radiation induced chromosomal breakage in cultured cell

Essential features found in NBS are microcephaly (99.7%), usually without retardation, typical facial appearance with a receding forehead, prominent midface with long nose and long philtrum, and a receding mandible. Important additional features are café au lait spots, vitiligo and clinodactyly and syndactyly. All NBS patients presented chromosomal instability, X-ray hypersensitivity and increased risk for malignancy. More than 50% developed B or T origin lymphomas before 18 year of age. Many patients have recurrent bacterial and viral respiratory infections (56%) associated with antibody deficiencies.

Ataxia Telangiectasia
Bloom syndrome

• 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.