Immunodeficiency and infections were determined in 100 consecutive patients with ataxia-telangiectasia (A-T) seen at the Johns Hopkins Ataxia-Telangiectasia Clinical Center. Immunoglobulin (Ig) deficiencies were common: IgG4 in 65%, IgA in 63%, IgG2 48%, IgE in 23%, and IgG in 18%. Lymphopenia occurred in 71% of patients, with reduction of B-lymphocytes in 75%, CD4 T lymphocytes in 69%, and CDS T lymphocytes in 51%. Increasing age was not associated with increased frequency or severity of immune abnormalities. Infections included frequent, recurrent upper and lower respiratory tract infections (otitis media in 46% patients, sinusitis in 27%, bronchitis in 19%, and pneumonia in 15%). Uncomplicated varicella infection occurred in 44% of patients. Systemic bacterial, severe viral, and opportunistic infections are uncommon in A-T, and the immune defect is rarely progressive. 
COMMENT. Despite significant immune system abnormalities, patients with A-T are not commonly subject to systemic bacterial, severe viral, and opportunistic infections. The progressive neurodegenerative process typical of A-T is not accompanied by a worsening immune defect with age. A-T, a neurocutaneous syndrome, results from a defect in DNA repair. The A-T gene (known as ATM, for AT ‘mutated’) has been mapped to chromosome 11 (llq22.3) (Charrow J. Neurocutaneous syndromes. In: Millichap JG, ed. Progress in Pediatric Neurology III, PNB Publishers;435-439).