USMLE | Pathology Review for USMLE

Question 159

A 32-year-old male presents to an acute care clinic with complaints of chest pain that is worse when he breathes in. The chest pain started about a day ago. A few hours ago he coughed up blood. Physical examination reveals some dullness to percussion in the left upper lobe and crackles are heard at that site. His only past medical history is that he broke his left tibia one week ago while skiing, and has had to wear a cast, which he reports has hindered his ability to get around like normal. Of the following, which laboratory test is most likely to be elevated?

A. D-Dimer
B. PTT
C. AST
D. Hct
E. Glucose

Answer for Question 159

Answer: A (D-dimer)

Explanation: The clinical scenario is consistent with a pulmonary thromboembolus, which can present with pleuritic chest pain and hemoptysis. A peripheral thromboembolus can produce an infarction of the lung, which would lead to the dullness to percussion and crackles. The immobility is a risk factor for deep venous thrombosis and resultant pulmonary thromboembolus. Of the laboratory tests listed, an elevated d-dimer is most associated with deep venous thrombi and a pulmonary thromboembolus. In a patient with anti-phospholipid antibody syndrome, an elevated PTT would be possible, and those patients are at risk for thrombi and embolism; however, the history does not otherwise suggest this condition, and it is only one of many conditions that could possibly predipose to thrombosis and embolism.

Question 160

A 23-year-old tall and thin male presents to the emergency room at 2 am, saying that he awoke due to a sudden pain in his chest that was worse when he breathed, and has had difficulty breathing since that time. Physical examination reveals hyperresonance to percussion on the left side of his chest, which is associated with decreased breath sounds and absence of tactile fremitus. Of the following, what is the most likely diagnosis?

A. Acute myocardial infarct
B. Aortic dissection associated with Marfan syndrome
C. Pneumothorax
D. Lobar pneumonia
E. Pulmonary thromboembolus

Answer for Question 160

Answer: C (Pneumothorax)

Explanation: The clinical presentation is classic for a spontaneous pneumothorax (tall thin young male with sudden onset pleuritic chest pain and dyspnea). Physical examination is likewise consistent with pneumothorax – the hyperresonance occurs because the pleural cavity is filled with air, as do the decreased breath sounds and absence of tactile fremitus, since the lung is displaced away from the chest wall by intervening air. Although tall and thin suggest Marfan syndrome, the physical examination is not consistent with an aortic dissection and hemothorax (especially the hyperresonance); also, the patient would be potentially in shock from blood loss if an aortic dissection were the cause of his symptoms. The physical examination is also not consistent with pulmonary thromboembolus, although the sudden onset of dyspnea and pleuritic chest pain could be consistent.

Question 161

A 16-year-old tall male is playing basketball with friends when he suddenly develops chest pain and shortness of breath. His friends take him to the emergency room where a physical examination reveals hyperresonance to percussion on the left side of his chest, which is associated with decreased breath sounds and absence of tactile fremitus. Of the following, what is the most likely underlying pathologic finding?

A. Ruptured pulmonary bleb
B. Inflammation of blood vessel
C. Tearing of large caliber blood vessel
D. Asymmetric thickening of myocardium
E. Thrombus in blood vessel

Answer for Question 161

Answer: A (Ruptured pulmonary bleb)

Explanation: The clinical presentation is classic for a spontaneous pneumothorax (tall young male with sudden onset chest pain and dyspnea). Physical examination is likewise consistent with pneumothorax – the hyperresonance occurs because the pleural cavity is filled with air, and the decreased breath sounds and absence of tactile fremitus, since the lung is displaced away from the chest wall by intervening air. Although tall and thin suggest Marfan syndrome, the physical examination is not consistent with an aortic dissection and hemothorax (especially the hyperresonance), and thus a tearing of large caliber blood vessel is not the finding; also, the patient would be potentially in shock from blood loss. Although patients with hypertrophic cardiomyopathy can present as sudden death, the history and physical examination findings are not consistent with the diagnosis (i.e., a patient with hypertrophic cardiomyopathy would not normally developed sudden chest pain and shortness of breath). The physical examination findings are not consistent with a vasculitis or pulmonary thromboembolus.

Question 150

A 27-year-old male, who is a college instructor, presents to an acute care clinic with complaints of a productive cough for 3 days, a fever, and occasional difficulty breathing with exertion. He has no significant past medical history and does not smoke. A chest x-ray reveals consolidation of the lower lobe of the right lung. Of the following, what is the most likely etiology for his clinical presentation?

A. Bacterial infection
B. Parasitic infection
C. Mycobacterial infection
D. Aspiration
E. Neoplasm

Answer for Question 150

Answer: A (Bacterial infection)

Explanation: The presentation (short duration of productive cough, fever, and dyspnea) in an individual with no past medical history and with consolidation of one lung lobe is consistent with a lobar pneumonia, which, in this situation, would be a community-acquired bacterial infection, or possibly a community acquired viral infection, which can also have consolidation of a lung lobe on x-ray. Lobar pneumonia is often bacterial in origin, and most commonly Streptococcus pneumoniae. Given his history, Mycobacterium tuberculosis is unlikely (i.e., he is not homeless, or otherwise living under conditions likely to expose him to tuberculosis). He has no risk factor for aspiration; and given his young age and lack of smoking history, a pulmonary neoplasm would be very unlikely.

Question 151

A 33-year-old female, who is a nurse at the hospital, presents to an acute care clinic with complaints of a productive cough for 2 days associated with shaking chills. She also reports a fever of 38.5 degrees Celsius. She has no significant past medical history and does not smoke. Her heart rate is 105 bpm, her respiratory rate is 26 breaths per minute, and her blood pressure is 82/61 mmHg, which is lower than normal for her. A chest x-ray reveals consolidation of the lower lobe of the left lung. A blood culture is positive. Of the following, which condition in her past medical history would represent the most important risk factor for her current presenting condition?

A. Fracture of the left tibia three years ago while skiing
B. Remote splenectomy after abdominal trauma
C. Head injury following rock climbing fall
D. Past episode of deep venous thrombosis
E. History of acute rheumatic fever

Answer for Question 151

Answer: B (Remote splenectomy after abdominal trauma)

Explanation: The presenting features (productive cough and fever) combined with the x-ray results are consistent with a community-acquired pneumonia, which would likely be a lobar pneumonia in this case. The most common bacterial etiologic agent for a lobar pneumonia is Streptococcus pneumoniae. Individuals without a spleen are at increased risk for the development of a pneumococcal sepsis as the spleen plays a role in the production of antibodies against polysaccharides, which protect against encapsulated organisms. The other conditions would be play a significant role in her development of pneumonia or resultant sepsis.

Question 152

A 24-year-old male who has smoked since he was 14 years old but has no other past medical history presents to an acute care clinic in July with complaints of a productive cough and fever to 38.4 degrees Celsius for the past 4 days. Physical examination reveals dullness to percussion on the lower left side of the chest and crackles are heard at this location. Of the following, what is the most likely diagnosis?

A. Community-acquired pneumonia
B. Chronic bronchitis
C. Pulmonary thromboembolus
D. Bronchogenic carcinoma
E. Aspiration pneumonia

Answer for Question 152

Answer: A (Community-acquired pneumonia)

Explanation: The presentation (cough and fever) and physical examination (dullness to percussion and crackles) are consistent with a community-acquired pneumonia. While chronic bronchitis can present with a productive cough, patients would normally be afebrile and there would be no localizing physical examination findings (i.e., the dullness to percussion or crackles). While a pulmonary thromboembolus could, with infarction, lead to a region of dullness to percussion and crackles, and could have a fever, the productive cough would not be typical and the patient has no risk factors for deep venous thrombi. Even though he has a smoking history, a bronchogenic carcinoma would be rare at this age. While aspiration pneumonia could cause the signs and symptoms listed, the patient has no risk factors for aspiration (e.g., a neuromuscular disease, or drug/alcohol intoxication).

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Questions 159-161: Lung pathology