Which of the following is not a common symptom of immunodeficiency disorders?

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.

Explanation: The correct answer is a. Severe combined immunodeficiency (SCID). SCID is a severe and rare primary immunodeficiency disorder characterized by the absence or severe impairment of both T and B cells, leading to a profound deficiency in cellular and humoral immunity.

Incorrect choices:

b. X-linked agammaglobulinemia (XLA) primarily affects B-cell function, resulting in a lack of mature B cells and low levels of immunoglobulins, but does not typically involve T-cell deficiency.

c. Wiskott-Aldrich syndrome affects platelet function and immune system regulation, but it is not characterized by a deficiency of both T and B cells.

d. Common variable immunodeficiency (CVID) is characterized by reduced levels of immunoglobulins, particularly IgG and IgA, but it does not typically lead to a complete deficiency of both T and B cells.