Aryan, a 14-year-old boy presented with chronic diarrhea and weight loss. History reveals thathe has repeated attacks of respiratory tract infections with Pseudomonas aeruginosa. His younger brother died from a severe respiratory infection at the age of 7. Which of the following agents is most likely to improve this patient’s condition?

**Core Concept**
The patient's condition is suggestive of a primary immunodeficiency disorder, specifically chronic granulomatous disease (CGD), characterized by recurrent infections with catalase-positive organisms like Pseudomonas aeruginosa. This is due to a defect in the NADPH oxidase system, leading to an inability to generate superoxides and kill ingested microbes.

**Why the Correct Answer is Right**
The patient's condition can be improved with the use of interferon-gamma (IFN-γ) therapy, which has been shown to enhance the oxidative burst in neutrophils and macrophages, thereby improving the patient's ability to kill ingested microbes. This is particularly beneficial in CGD patients who have a defect in the NADPH oxidase system. IFN-γ works by activating the phagocytes and increasing the expression of inducible nitric oxide synthase (iNOS), which produces nitric oxide (NO) that kills the microbes.

**Why Each Wrong Option is Incorrect**
**Option A:** Antibiotics would be beneficial in treating acute infections but would not address the underlying defect in the NADPH oxidase system.
**Option B:** Immunoglobulin replacement therapy is used in patients with antibody deficiencies, not in CGD patients who have a defect in phagocytic function.
**Option C:** Corticosteroids are used to suppress inflammation but would not improve the patient's ability to kill ingested microbes.

**Clinical Pearl / High-Yield Fact**
CGD patients are particularly susceptible to infections with catalase-positive organisms like Pseudomonas aeruginosa, Staphylococcus aureus, and Aspergillus spp. They also have an increased risk of developing granulomatous complications like abscesses and fistulas.

**Correct Answer:** C. Interferon-gamma (IFN-γ) therapy.

✓ Correct Answer: B. Pancreatic lipase