A 70-year-old man presents with a complaint of difficulty walking. He has a history of Parkinson's disease and is currently taking levodopa. On examination, he has rigidity, bradykinesia, and a shuffling gait. Which of the following is the most likely cause of his symptoms?

Correct Answer: A

Rationale: The correct answer is A: Parkinson's disease progression. This is the most likely cause of the patient's symptoms due to his history of Parkinson's disease and the presence of typical Parkinsonian features such as rigidity, bradykinesia, and shuffling gait. Levodopa is a common medication used to manage symptoms of Parkinson's disease. The progression of Parkinson's disease can lead to worsening motor symptoms over time, including difficulty walking. Option B: Normal aging is incorrect because the patient's symptoms are not solely due to the aging process, but rather are consistent with the known condition of Parkinson's disease. Option C: Cerebellar ataxia is unlikely as the patient's symptoms align more closely with Parkinsonian features rather than cerebellar dysfunction. Option D: Spinal cord compression is not the most likely cause as the patient's symptoms are more characteristic of Parkinson's disease progression rather than symptoms typically associated with spinal cord compression.

Correct Answer: A

Rationale: The correct diagnosis is A: Sarcoidosis. In this case, the key features are bilateral hilar lymphadenopathy, shortness of breath, dry cough, smoking history, and frequent sinus infections. Sarcoidosis commonly presents with these symptoms and radiographic findings. Hilar lymphadenopathy is a classic feature of sarcoidosis due to granuloma formation. Lung cancer (B) is less likely given the presentation and the absence of lung mass on imaging. Pneumonia (C) typically presents with consolidations on chest X-ray, which is not seen in this case. Chronic obstructive pulmonary disease (D) is characterized by airflow limitation and does not typically present with hilar lymphadenopathy.

Correct Answer: A

Rationale: The correct diagnosis is A: Myocardial infarction. The ST-segment elevation in leads II, III, and aVF on the ECG indicates an inferior wall myocardial infarction. This presentation, along with the patient's age, history of coronary artery disease, and diabetes mellitus, strongly suggests myocardial infarction. Angina (B) typically presents with transient chest pain that is relieved with rest or medication. Pulmonary embolism (C) presents with sudden-onset dyspnea and chest pain, often accompanied by tachycardia. Aortic dissection (D) commonly presents with severe tearing chest pain radiating to the back, not ST-segment elevation on ECG.

Correct Answer: B

Rationale: The positive Babinski sign indicates upper motor neuron dysfunction. When the sole of the foot is stroked, the big toe extends upward instead of curling down. This suggests damage to the corticospinal tract, characteristic of upper motor neuron lesions. Choices A, C, and D are incorrect because a positive Babinski sign is not a normal finding in adults, not related to peripheral neuropathy, and not indicative of cerebellar dysfunction.

Correct Answer: B

Rationale: The correct answer is B: Pleuritis. A pleural friction rub is caused by the inflammation of the pleural surfaces rubbing against each other during breathing. Pleuritis is the most likely cause as it directly involves inflammation of the pleura. Pneumonia (choice A) typically presents with crackles or decreased breath sounds. Pulmonary embolism (choice C) may present with pleuritic chest pain but not a friction rub. Chronic obstructive pulmonary disease (COPD) (choice D) is characterized by wheezing and decreased breath sounds, not a friction rub. Pleuritis is the only choice directly related to the inflammation of the pleura, leading to a pleural friction rub.