What type of immunodeficiency results primarily in low T cell counts due to thymic hypoplasia?

What type of immunodeficiency results primarily in low T cell counts due to thymic hypoplasia?

• A. DiGeorge's syndrome
• B. Common variable immunodeficiency
• C. X-linked agammaglobulinemia
• D. Chronic granulomatous disease

Answer: (A)

DiGeorge's syndrome is characterized by a developmental defect of the third and fourth pharyngeal pouches, leading to underdevelopment of the thymus gland. This condition results in thymic hypoplasia, which directly impacts the development of T cells. Since the thymus is essential for the maturation of T cells, individuals with DiGeorge's syndrome exhibit significantly reduced T cell counts, which contributes to their increased susceptibility to infections. In contrast, other immunodeficiencies listed do not primarily affect T cell counts in the same way. Common variable immunodeficiency involves impaired antibody production rather than T cell development. X-linked agammaglobulinemia affects B cells, leading to low immunoglobulin levels without specifically impacting T cell numbers. Chronic granulomatous disease primarily affects phagocytic cells and their ability to combat certain infections, and while it can involve T cell responses, it does not originate from thymic issues causing low T cell counts. Thus, the relationship between DiGeorge's syndrome and low T cell counts due to thymic hypoplasia makes it the correct answer.

DiGeorge's syndrome is characterized by a developmental defect of the third and fourth pharyngeal pouches, leading to underdevelopment of the thymus gland. This condition results in thymic hypoplasia, which directly impacts the development of T cells. Since the thymus is essential for the maturation of T cells, individuals with DiGeorge's syndrome exhibit significantly reduced T cell counts, which contributes to their increased susceptibility to infections.

In contrast, other immunodeficiencies listed do not primarily affect T cell counts in the same way. Common variable immunodeficiency involves impaired antibody production rather than T cell development. X-linked agammaglobulinemia affects B cells, leading to low immunoglobulin levels without specifically impacting T cell numbers. Chronic granulomatous disease primarily affects phagocytic cells and their ability to combat certain infections, and while it can involve T cell responses, it does not originate from thymic issues causing low T cell counts.

Thus, the relationship between DiGeorge's syndrome and low T cell counts due to thymic hypoplasia makes it the correct answer.