ANSWERS OF MCQS PUBLISHED ON 3/9/2019

ANSWERS

MCQ#01

B

IgA deficiency is the most common primary immunodeficiency, occurring in approximately 1 in 600 people. While most people with selective IgA deficiency are asymptomatic, some develop recurrent infections at mucosal barriers, such as the respiratory and gastrointestinal tracts.

Some patients with IgA deficiency develop anti-IgA antibodies and are at risk for anaphylaxis when they receive any blood product containing IgA, the most common of which is pooled intravenous immunoglobulin.

MCQ#02

C

Given the chronic recurrent respiratory tract infections in an otherwise healthy child with arthritis, this patient is likely to have IgA deficiency. The relationship of autoimmune disease and IgA deficiency has been well described, particularly with juvenile idiopathic arthritis and celiac disease. There is no treatment for IgA deficiency and treatment of the arthritis will not improve IgA production. Given the destructive nature of untreated JIA, the medication cannot be stopped. More aggressive treatment for arthritis, such as with methotrexate, steroids, or biologic agents will lead to further immunosuppression and the patient will need to be monitored for infection and treated aggressively when present.

MCQ#03

A

Disorders of the alternative complement pathway and terminal complement deficiencies have all been associated with increased risk of pyogenic infections, particularly Neisseria. Terminal complement component deficiencies, such as C5

deficiency lead to infection by affecting the ability to make a membrane attack complex and thereby lyse the bacteria. Disorders of the classical pathway can lead to infection, but are more commonly associated with autoimmune disease, particularly systemic lupus erythematosus.

MCQ#04

A

The genetic defect in AT, the ATM gene, leads to impairment of DNA repair. Patients with AT are thus highly sensitive to ionizing radiation, and are at significantly increased risk for developing malignancies, particularly of lymphoid origin. Exposure of patients to ionizing radiation or radiomimetic agents should be strictly limited, including standard radiography.

MCQ#05

D

Disorders of B-cell development result in maturation arrest of B cells and lack of mature B cells in the peripheral circulation. This condition results in agammaglobulinemia. The affected child depends on maternal immunoglobulin for humoral immune system protection; however, once maternal immunoglobulin decays (typically by 6 months of age), the child has no protection against infections with encapsulated bacteria or viruses, such as enterovirus, leading to chronic recurrent infection.