USMLE Answer 29

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29. The correct answer is D. Patients with selective IgA deficiency may have circulating antibodies to IgA. Fatal anaphylaxis may ensue if they are transfused with blood products with serum containing IgA, although many patients with selective IgA deficiency are asymptomatic and never diagnosed. Symptomatic patients may have recurrent sinopulmonary infections and diarrhea, as well as an increased incidence of autoimmune and allergic diseases.

AIDS (choice A) predisposes for infections and neoplasms, but not anaphylaxis.

C1 esterase inhibitor deficiency (choice B) is an autosomal dominant disease characterized by recurrent attacks of colic and episodes of laryngeal edema, without pruritus or urticarial lesions. This disorder is also known as hereditary angioedema.

DiGeorge syndrome (choice C) is characterized by thymic aplasia and, sometimes, hypoparathyroidism. The disorder is due to abnormal development of the third and fourth pharyngeal arches.

Wiskott-Aldrich syndrome (choice E) is a form of immunodeficiency associated with thrombocytopenia and eczema.