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

Explanation: The correct answer is d. Selective IgA deficiency. This disorder is characterized by a lack of immunoglobulin A, which can lead to an increased susceptibility to infections, particularly in the respiratory and gastrointestinal tracts.

Incorrect choices:

a. Selective IgM deficiency is a rare immunodeficiency disorder characterized by a lack of immunoglobulin M (IgM), not IgA.

b. X-linked agammaglobulinemia is a primary immunodeficiency disorder caused by a mutation in the BTK gene, resulting in a deficiency of B cells and immunoglobulins.

c. Common variable immunodeficiency (CVID) is a heterogeneous group of disorders characterized by decreased levels of immunoglobulins, including IgA, IgG, and IgM.

Explanation: The correct answer is b. Primary immunodeficiency disorders result from a genetic or inherited defect, while secondary immunodeficiency disorders are caused by external factors, such as infections or medications.

Incorrect choices:

a. Primary immunodeficiency disorders are present from birth and are usually genetic or inherited, while secondary immunodeficiency disorders can be acquired later in life due to external factors.

c. The manifestations and systems affected by primary and secondary immunodeficiency disorders can vary widely and are not limited to specific areas of the body.

d. Secondary immunodeficiency disorders are more common than primary immunodeficiency disorders, as they can be caused by various factors and are often associated with other medical conditions.