Question

A child was found to have deficiency of ADA enzyme. The complete blood count of this child will show:

• A. High count of lymphocytes
• B. Low count of B lymphocytes
• C. Low count of T lymphocytes
• D. Both b and c

Answer 1

The correct option is D Both b and c

Adenosine deaminase (ADA) enzyme is produced in all cells, however, excessively expressed in the lymphocytes which is crucial for the immune system to function.

In ADA deficiency, the body makes insufficient ADA enzyme. This leads to the buildup of the toxic byproduct which can impair the production of immune cells (lymphocytes). This can cause severe combined immunodeficiency disease (SCID).

These patients with ADA deficiency have non-functional lymphocytes and so they cannot mount immune responses against invading pathogens. Complete blood count of ADA-deficient individuals will reflect depletion of T-lymphocytes and B-lymphocytes.