Which of the following clinical manifestations is a common symptom of primary immunodeficiency disorders?

Explanation: The correct answer is b. DiGeorge syndrome. This disorder is caused by a deletion in chromosome 22, resulting in the underdevelopment of the thymus and parathyroid glands. It leads to impaired T cell function and is associated with developmental delays, chronic infections, and autoimmune problems.

Incorrect choices:

a. X-linked agammaglobulinemia is a primary immunodeficiency disorder that primarily affects B cell function, leading to a deficiency of immunoglobulins (antibodies).

c. Wiskott-Aldrich syndrome is an X-linked recessive disorder characterized by a triad of symptoms: eczema, thrombocytopenia (low platelet count), and immunodeficiency.

d. Severe combined immunodeficiency (SCID) is a group of rare disorders characterized by a severe deficiency of T cells, B cells, and natural killer (NK) cells.

Explanation: The correct answer is b. Common variable immunodeficiency (CVID). CVID is an example of a primary immunodeficiency disorder, which is typically caused by genetic mutations affecting the immune system's development and function.

Incorrect choices:

a. Human immunodeficiency virus (HIV) infection is an example of a secondary immunodeficiency disorder, which occurs due to an external factor, such as a viral infection, damaging the immune system.

c. Rheumatoid arthritis is an autoimmune disorder that affects the joints and is not classified as an immunodeficiency disorder.

d. Diabetes mellitus is a metabolic disorder involving insulin production and does not directly affect the immune system's function.