Which statement about thymic involvement in DiGeorge syndrome is correct?

• A. DiGeorge syndrome involves thymic hypoplasia leading to T-lymphocyte deficiency
• B. Thymic hyperplasia is typical
• C. Thymus is unaffected
• D. Thymus cannot be evaluated clinically

Answer: (A)

Thymic development abnormalities in DiGeorge syndrome lead to a T-cell immunodeficiency because the thymus is essential for educating and maturing T lymphocytes. When the thymus is underdeveloped (hypoplasia or aplasia), there are far fewer mature T cells, causing impaired cellular immunity and greater susceptibility to infections in infancy. This is why thymic hypoplasia with T-lymphocyte deficiency is the correct statement. Thymic hyperplasia is not typical in this condition, and the thymus is not generally unaffected—the deficiency stems from its underdevelopment. Clinically, thymic status can be evaluated through imaging and immune testing (such as T-cell counts and flow cytometry or TRECs), so it isn’t true that the thymus cannot be evaluated.