What are the flow cytometry findings characteristic of ADA deficiency?

In the context of Adenosine Deaminase (ADA) deficiency, flow cytometry findings typically reveal significant alterations in lymphocyte populations. ADA deficiency leads to an impairment in T-cell development due to the accumulation of toxic metabolites, which primarily affects the thymus.

The characteristic findings associated with ADA deficiency include low levels of T cells, indicated by low CD3 expression, which corresponds to the diminished number of T lymphocytes due to their failure to mature properly. Similarly, the B-cell population, marked by CD19, is also significantly reduced, reflected in low CD19 expression. This further indicates disruption in the lymphocyte development pathway.

The levels of natural killer (NK) cells, indicated by CD56, may also be low but can vary. However, in severe cases of ADA deficiency, a marked reduction in all three populations—CD3, CD19, and CD56—is often observed.

The combination of low CD19, low CD3, and low CD56 depicts the characteristic immunophenotype seen in individuals with ADA deficiency, emphasizing the severe impact of the condition on the immune system.