Correct Answer: C

Rationale: The correct answer is C. In assessing a child for migraines, asking about food allergies is least likely to yield data that will confirm or rule out migraines as the cause of his headaches. Food allergies are unrelated to the typical symptoms and triggers of migraines, such as family history, associated symptoms like nausea and vomiting, and pain-free intervals between headaches. Therefore, in this scenario, focusing on food allergies is less relevant for identifying migraines as the cause of the boy's headaches.

Correct Answer: A

Rationale: The correct answer is hematuria. Hematuria, which is the presence of blood in the urine, is a common sign associated with benign prostatic hypertrophy (BPH). It can occur due to irritation or damage to the prostate tissue. While urinary frequency and erectile dysfunction can also be seen in BPH patients, hematuria is more specifically linked to prostate issues. Flank pain is not typically a direct symptom of BPH.

Correct Answer: B

Rationale: The correct answer is B. Finasteride (Proscar) is used in the treatment of benign prostatic hyperplasia to improve urinary flow and decrease symptoms of urinary retention by reducing the size of the prostate gland. Choice A is incorrect because although finasteride may reduce the size of the prostate gland, the expected outcome relevant to the patient's symptoms is improved urinary flow rather than a specific change in gland size. Choice C is incorrect because finasteride actually decreases the production of prostate-specific antigen (PSA) due to its mechanism of action. Choice D is incorrect because although improved urinary flow may lead to a reduction in nocturnal awakenings, the main expected outcome of finasteride treatment is related to urinary symptoms.

Correct Answer: C

Rationale: The correct answer is C: Serum sickness. Serum sickness is characterized by the formation of immune complexes in response to certain medications or proteins. These immune complexes can deposit in tissues, leading to inflammation and tissue damage. Bronchial asthma (Choice A) is a chronic inflammatory condition of the airways not primarily mediated by immune complexes. Contact dermatitis (Choice B) is a type IV hypersensitivity reaction mediated by T cells, not immune complexes. Rheumatoid arthritis (Choice D) is an autoimmune disease where antibodies target self-antigens, but it is not primarily mediated by immune complexes.

Correct Answer: A

Rationale: The correct answer is A: Active tuberculosis. Given the patient's history of homelessness and initiation of isoniazid (INH) treatment, the most likely diagnosis is active tuberculosis. Isoniazid is a first-line medication used in the treatment of active tuberculosis. Latent tuberculosis (choice B) would not typically necessitate treatment with isoniazid alone. Mycobacterium avium complex (choice C) is not typically treated with isoniazid alone. Human immunodeficiency virus (choice D) is a risk factor for developing tuberculosis but is not the primary diagnosis in this patient scenario.