Question

A boy child is suffering from severe weight loss and malnutrition. He was found to have an ADA deficiency. The complete blood count of this child will show:

• A. High count of B and T lymphocytes
• B. Low count of B and T lymphocytes
• C. Low count of erythrocytes
• D. Blood count is not affected in ADA deficiency

Answer 1

The correct option is B Low count of B and T lymphocytes

The mutation of the gene coding for the enzyme adenosine deaminase (ADA) can cause SCID (Severe Combined Immunodeficiency). ADA is involved in purine metabolism. When DNA is broken down, it generates a molecule known as deoxyadenosine which is toxic to lymphocytes. The enzyme ADA is crucial for the immune system to function as it is involved in the conversion of deoxyadenosine to a non-toxic molecule called deoxyinosine.
In the case of ADA deficiency, the body makes insufficient ADA. This leads to the buildup of the toxic byproduct and can cause severe combined immunodeficiency (SCID). So, the complete blood count of ADA-deficient individuals will show depletion of T lymphocytes, B lymphocytes, and Natural Killer cells.