Which of the following is a characteristic of osteosarcoma?

Correct Answer: C

Rationale: Osteosarcoma is an aggressive bone tumor that most commonly arises in the bone marrow of long bones, such as the femur or tibia. Choice A is incorrect as osteosarcoma is not a slow-growing tumor but rather a fast-growing one. Choice B is incorrect as osteosarcoma is not typically solitary but can involve multiple lesions. Choice D is incorrect as osteosarcoma primarily affects the medullary (marrow) cavity of bones, rather than infiltrating the trabeculae in spongy bone and surrounding tissue.

Correct Answer: C

Rationale: In nephritic syndrome, the presence of red blood cell casts in the urine is a characteristic finding, reflecting glomerular inflammation and damage. This differentiates it from nephrotic syndrome, where red blood cell casts are typically absent. Choice A is incorrect because nephritic syndrome usually presents with less albuminuria compared to nephrotic syndrome. Choice B is incorrect as hematuria is a common feature of nephritic syndrome. Choice D is incorrect as hypoalbuminemia is more commonly associated with nephrotic syndrome.

Correct Answer: C

Rationale: Benign positional vertigo is typically triggered by changes in head position, such as bending forward or turning over in bed. This change in position leads to brief episodes of vertigo, often associated with nystagmus, which is rapid, involuntary eye movements. Pupillary changes and headaches are not typical features of benign positional vertigo, making choices B and A incorrect. Nystagmus in benign positional vertigo usually stops when the eyes fixate on an object, so choice D is also incorrect.

Correct Answer: B

Rationale: Acute closed-angle glaucoma presents with symptoms such as a red eye, severe pain, and rapid visual acuity changes due to increased intraocular pressure. This condition is considered an ophthalmologic emergency. Bacterial conjunctivitis typically presents with redness, discharge, and irritation but is not associated with severe pain or visual changes. Chronic open-angle glaucoma is usually asymptomatic until advanced stages and does not typically present with acute pain. Blepharitis involves inflammation of the eyelid margins and is characterized by redness and irritation, but it does not cause severe pain or acute visual changes.

Correct Answer: B

Rationale: Muscular dystrophy is primarily caused by mutations in the gene that provides instructions for making the protein dystrophin. Dystrophin plays a crucial role in maintaining the structure of muscle fibers. Glycoprotein is a general term for proteins with sugar molecules attached, not specifically related to muscular dystrophy. Troponin is a protein involved in muscle contraction regulation, and actinomyosin is not a specific muscle protein but a complex formed during muscle contraction. Therefore, the correct answer is dystrophin.

Correct Answer: B

Rationale: Postoperative adhesions are a common cause of mechanical small intestine obstruction. Adhesions can form after abdominal surgery, causing bands of scar tissue that may twist or pull the intestines, leading to obstruction. This is a more common cause compared to infection, tumors, or foreign bodies. Infection may lead to inflammation but is not a typical cause of mechanical obstruction. Tumors and foreign bodies can cause blockages but are less common than postoperative adhesions.

Correct Answer: A

Rationale: Alpha-1 antitrypsin deficiency is a genetic cause of chronic obstructive pulmonary disease (COPD). It is more common in younger patients with a history of smoking at a younger age, like the 30-year-old who has smoked for 3 years. Choices B, C, and D are less likely to be associated with alpha-1 antitrypsin deficiency as COPD in these cases is more likely due to smoking and environmental exposures.

Correct Answer: A

Rationale: Abrupt withdrawal or discontinuation of prednisone, a corticosteroid, can lead to adrenal crisis. This occurs due to the suppression of the adrenal glands' natural cortisol production caused by prolonged exogenous steroid administration. Adrenal crisis presents with symptoms such as weakness, fatigue, abdominal pain, and hypotension. Hypercortisolism (Cushing syndrome) results from chronic excessive exposure to cortisol, not abrupt withdrawal. ACTH stimulation would be expected in response to low cortisol levels, not as a direct consequence of prednisone withdrawal. Thyroid crisis (thyroid storm) is associated with severe hyperthyroidism and is not directly related to corticosteroid withdrawal.

Correct Answer: D

Rationale: Palpable kidneys are a common clinical manifestation in patients with polycystic kidney disease due to the enlarged kidneys with multiple cysts. Suprapubic pain is not typically associated with this condition. Periorbital edema is more commonly seen in conditions like nephrotic syndrome. A low serum creatinine level is not a typical finding in renal impairment, as impaired kidneys usually lead to an elevated serum creatinine level.