Which of the following clinical manifestations is often observed in individuals with severe combined immunodeficiency (SCID)?

Explanation: The correct answer is b. Common variable immunodeficiency (CVID). CVID is a primary immunodeficiency disorder characterized by a reduced level of immunoglobulins, particularly IgA, leading to an increased susceptibility to infections.

Incorrect choices:

a. Severe combined immunodeficiency (SCID) is a more severe immunodeficiency disorder that affects multiple components of the immune system, not specifically IgA levels.

c. DiGeorge syndrome is caused by a genetic abnormality and is characterized by a defect in the development of certain organs, including the thymus and parathyroid glands. It may result in immune system abnormalities but does not primarily involve IgA deficiency.

d. Wiskott-Aldrich syndrome is a rare X-linked genetic disorder that affects platelet function and immune system regulation but is not specifically associated with IgA deficiency.

Explanation: The correct answer is c. Primary immunodeficiency disorders are typically present at birth or during early childhood and are caused by genetic defects that affect the function of the immune system. They are not acquired later in life due to environmental factors.

Incorrect choices:

a. Primary immunodeficiency disorders are not acquired later in life; they are usually genetic and present from birth.

b. Primary immunodeficiency disorders are characterized by a weakened or deficient immune response, not an overactive immune response.

d. Primary immunodeficiency disorders are often not easily treatable with antibiotics and antiviral medications because they result from genetic defects in the immune system.