Review Question - QID 109226

The patient in this vignette presents with failure to thrive, short stature, a skin abscess, and an abnormal dihydrorhodamine flow cytometry suggestive of chronic granulomatous disease (CGD). Patients with CGD are at an increased risk of infections with catalase-positive organisms such as Aspergillus fumigatus.

CGD is a primary immunodeficiency syndrome caused by a deficiency in NADPH oxidase. This defect impairs the ability of neutrophils to generate reactive oxygen species during a respiratory burst. Without NADPH oxidase, neutrophils must rely on using peroxide generated by microorganisms; however, catalase-positive species such as Staph aureus, E. coli, P. aeruginosa, and others can neutralize their own peroxidase via catalase. Flow cytometry reduction of dihydrorhodamine will be abnormal in patients with CGD as this test measures the activity of NADPH oxidase.

Incorrect Answers:
Answer 2: Members of the enterococcus family are catalase-negative. Patients with CGD are not at an increased risk of infections due to enterococci.

Answer 3: Giardia lamblia is a protozoan that typically causes fatty, foul-smelling diarrhea. It does not demonstrate significant catalase activity. Patients with CGD are therefore not at an increased risk of infections due to Giardia lamblia.

Answers 4 & 5: Members of the streptococcus family are all catalase-negative. Patients with CGD are not at an increased risk of infections due to streptococci.

Bullet Summary:
Chronic granulomatous disease is caused by a deficiency in NADPH oxidase leading to an increased susceptibility to catalase-positive organisms such as Aspergillus fumigatus.