Correct Answer: B

Rationale: DiGeorge syndrome is caused by a congenital lack of thymic tissue, which plays a crucial role in T cell development and maturation, leading to immune deficiency. Choice A is incorrect because DiGeorge syndrome primarily affects T cells, not B cells. Choice C is incorrect as it is too broad and not specific to the thymus. Choice D is incorrect as selective IgG deficiency is a different condition unrelated to DiGeorge syndrome.

Correct Answer: C

Rationale: Intravenous amphotericin can cause nephrotoxicity, leading to increased blood urea nitrogen levels. Elevated blood urea nitrogen (BUN) indicates impaired renal function, which is a known adverse effect of amphotericin. Therefore, a BUN level of 60 mg/dL warrants the discontinuation of the antifungal agent. The other options, such as a sodium level of 138 mEq/L, hematocrit of 39%, and AST level of 10 Unit/L, are within normal ranges and not indicative of the need to discontinue amphotericin therapy.

Correct Answer: B

Rationale: The correct answer is B: 'Use of nitrates.' Sildenafil (Viagra) is contraindicated in patients taking nitrates due to the risk of severe hypotension. Nitrates and sildenafil both act as vasodilators, and their combined use can lead to a dangerous drop in blood pressure. Choices A, C, and D are incorrect because having a history of hypertension, using antihypertensive medications, or having a history of peptic ulcer disease are not key contraindications for sildenafil use.

Correct Answer: C

Rationale: The correct answer is C: An inflammatory process in the testicles. Secondary hypogonadism in males can be caused by various factors, including an inflammatory process in the testicles. Mumps (choice B) can lead to orchitis but is less common in adults. Type 1 diabetes (choice A) is not a common cause of secondary hypogonadism. Testicular trauma (choice D) can cause primary hypogonadism but is less likely to cause secondary hypogonadism.

Correct Answer: B

Rationale: The correct answer is B because consistent intake of prescribed drugs is crucial for curing tuberculosis. By emphasizing the necessity of following the treatment plan, the patient is more likely to achieve a successful outcome. Choice A is incorrect because it focuses on the risk of adverse effects rather than the primary goal of TB cure. Choice C is incorrect as it does not address the issue of inconsistent drug intake. Choice D is also incorrect as it introduces a different treatment (antiretrovirals) not relevant to latent tuberculosis.