What is the role of lab tests in the workup of ataxia-telangiectasia (A-T)?

Updated: Apr 06, 2020
  • Author: Camila K Janniger, MD; Chief Editor: Dirk M Elston, MD  more...
  • Print
Answer

Laboratory markers are important for both diagnosis and prognosis. The most constant markers are elevated levels of alpha-fetoprotein (AFP) and carcinoembryonic antigen and chromosomal abnormalities, especially inversions and translocations involving chromosomes 7 and 14, though neither of these abnormalities is always found and their demonstration requires specific techniques available in only a few centers.

The demonstration of humoral or cellular immunologic defects may also permit an early diagnosis, although such defects are nonspecific and present less frequently.

The dysgammaglobulinemia of ataxia-telangiectasia includes an absent or low level of immunoglobulin A (IgA), including secretory IgA; a normal or low level of immunoglobulin G (IgG); and an elevated or normal level of immunoglobulin M (IgM). Elevated IgM is evident in only 60% of patients. [7] IgA deficiency is found in about 70% of patients with ataxia-telangiectasia syndrome. A deficit in IgG2 and IgG4 subclasses has been demonstrated in several patients, and IgE may also be absent or low.

Defects of cellular immunity include a low lymphocyte count, a poor response to skin tests to common antigens, low T-lymphocyte proliferation in the presence of mitogens, and deficient antibody production to viral or bacterial antigens. Excessive T-cell suppressor activity and intrinsic B-cell defects have been described in some patients, suggesting disturbances of immunoregulatory mechanisms. The incidence of immunologic abnormalities increases with the age of the patients.


Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!