3. In an evaluation of an 8-year-old boy who has had recurrent infections since the first year of life, findings include enlargement of the liver and spleen, lymph node inflammation, and a superficial dermatitis resembling eczema. Microscopic examination of a series of peripheral blood smears taken during the course of a staphylococcal infection indicates that the bactericidal capacity of the boy’s neutrophils is impaired or absent. What is the most likely cause of this child’s illness? a. Defect in the enzyme NADPH oxidase b. Defect in the enzyme adenosine deaminase (ADA) c. Defect in the IL-2 receptor d. Developmental defect at the pre-B stage e. Developmental failure of pharyngeal pouches 3 and 4 4.

MCQ3 

In an evaluation of an 8-year-old boy who has had recurrent infections
since the first year of life, findings include enlargement of the liver and
spleen, lymph node inflammation, and a superficial dermatitis resembling
eczema. Microscopic examination of a series of peripheral blood smears
taken during the course of a staphylococcal infection indicates that the bactericidal
capacity of the boy’s neutrophils is impaired or absent. What is the
most likely cause of this child’s illness?


a. Defect in the enzyme NADPH oxidase
b. Defect in the enzyme adenosine deaminase (ADA)
c. Defect in the IL-2 receptor
d. Developmental defect at the pre-B stage
e. Developmental failure of pharyngeal pouches 3 and 4



AnswerThe answer is a. (Cotran, pp 65, 231–236. Rubin, pp 67, 1088.)
Patients with chronic granulomatous disease have defective functioning of
phagocytic neutrophils and monocytes due to an inability to produce
hydrogen peroxide. That is, their phagocytic cells have a decreased oxidative
or respiratory burst. The most common cause of chronic granulomatous
disease is defective NADPH oxidase, which is an enzyme on the
membrane of lysosomes that converts O2 to superoxide and stimulates
oxygen burst. This deficiency results in recurrent infections with catalasepositive
organisms, such as S. aureus. The classic form of chronic granulomatous
disease usually affects boys and causes death before the age of 10.
Key findings in chronic granulomatous disease include lymphadenitis,
General Pathology Answers 81
hepatosplenomegaly, eczematoid dermatitis, pulmonary infiltrates that are
associated with hypergammaglobulinemia, and defective ability of neutrophils
to kill bacteria.
A defect in the enzyme adenosine deaminase (ADA) is seen in the
autosomal recessive (Swiss) form of severe combined immunodeficiency
disease (SCID), while a defect in the IL-2 receptor is seen in the X-linked
recessive form of SCID. A developmental defect at the pre-B stage is seen in
X-linked agammaglobulinemia of Bruton, while developmental failure of
pharyngeal pouches 3 and 4 is characteristic of DiGeorge’s syndrome.