Which of the following statements accurately describes immunodeficiency disorders?

The correct answer is c. Ataxia-telangiectasia. Ataxia-telangiectasia is a rare genetic disorder that affects the cerebellum, causing poor muscle coordination (ataxia) and small, dilated blood vessels (telangiectasias). It also leads to defective T-cell function, making affected individuals more susceptible to infections.

Incorrect choices:

a. X-linked agammaglobulinemia (XLA) is a primary immunodeficiency disorder that primarily affects B-cell function, leading to a lack of mature B cells and low levels of immunoglobulins, but does not involve defective T-cell function.

b. Selective immunoglobulin A (IgA) deficiency is characterized by a deficiency of IgA, but it does not typically lead to defective T-cell function.

d. DiGeorge syndrome is caused by a deletion on chromosome 22 and primarily affects the development of certain organs, including the thymus and parathyroid glands, resulting in T-cell deficiency. While it may lead to some B-cell abnormalities, defective T-cell function is the hallmark of this disorder.

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.