February 15, 2020 | Pathology Review for USMLE

Questions 156-158: Lung pathology

Question 156

A 29-year-old male presents to an acute care clinic with complaints of a productive cough and fever to 38.7 degrees Celsius for the past 3 days, associated with some chest pain when he breaths and with chills. Physical examination reveals dullness to percussion on the left side of the chest. Crackles and a pleural rub are also heard at this location. A chest x-ray reveals consolidation of the left lung. A sputum culture is obtained and grows a pure sample of gram positive cocci in chains. Of the following, laboratory testing of this organism would reveal which of the following traits?

A. Not inhibited by optochin
B. Beta hemolytic
C. Bile soluble
D. Non-fermenter of glucose
E. Catalase positive

Answer for Question 156

Answer: C (Bile soluble)

Explanation: The presenting features are consistent with a community acquired pneumonia, consistent with a lobar pneumonia. A common cause of a lobar pneumonia is Streptococcus pneumoniae, which is gram positive and grows in chains. Streptococcus pneumoniae is bile soluble. It is also inhibited by optochin, alpha hemolytic, a fermenter of glucose, and catalase negative.

Question 157

Following a four day illness that was characterized by a high fever (up to 41 degrees Celsius) and severe muscle aches, a 29-year-old male presents to the emergency room with complaints of dyspnea with exertion, chest pain which is worse with expiration, and a productive cough. Physical examination reveals dullness to percussion on the left side of the chest. Crackles and a pleural rub are also heard at this location. A chest x-ray reveals consolidation of the left lung. A sputum culture is obtained and grows a pure sample of gram positive cocci in clusters. Of the following, laboratory testing of this organism would reveal which of the following traits?

A. Catalase negative
B. Coagulase positive
C. Alpha hemolysis
D. Non-fermenter of glucose

Answer for Question 157

Answer: B (Coagulase positive)

Explanation: The preceding illness has features of influenza (high fever and myalgias). One complication of influenza is the subsequent development of a secondary bacterial infection. In this situation, the patient developed Staphylococcus aureus, which is a common etiologic agent of a secondary bacterial infection in patients with influenza. Staphylococcus aureus is coagulase positive. It is also catalase positive, beta hemolytic and a fermenter of glucose.

Question 158

A 73-year-old male with the history of a stroke 2 years ago that left him with residual motor difficulties in eating is brought to the emergency room by his family because over the past three weeks he had developed a productive cough with foul-smelling sputum. In addition, he has lost about 10 lb. and has an intermittent fever (although his temperature wasn’t taken). He has no history of tobacco use. A chest x-ray reveals an infiltrate in the lower lobe of the right lung. Of the following, what is the most likely diagnosis?

A. Community acquired bacterial pneumonia
B. Community acquired viral pneumonia
C. Aspiration pneumonia
D. Mycobacterium tuberculosis
E. Necrotic pulmonary neoplasm

Answer for Question 158

Answer: C (Aspiration pneumonia)

Explanation: Elderly individuals, especially those with a history of a condition that would cause neuromuscular impairment, such as a stroke, are at risk for aspiration pneumonia. Because aspiration pneumonia often involves anaerobic bacteria and/or abscess formation, the patient can produce foul-smelling sputum. With aspiration pneumonia, patients often present over weeks or months and can have fever and weight loss. The lower lobes are affected, and more often the right side than the left side as the angle of the right bronchus allows for aspirated material to more easily enter the right lung.

Questions 153-155: Lung pathology

Question 153

A 29-year-old female presents to an acute care clinic with complaints of a productive cough and fever to 38.6 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. A chest x-ray reveals consolidation of the lower lobe of the left lung. A sputum culture grows Streptococcus pneumoniae. Of the following, which is the most responsible for the physical examination findings?

A. Collapse of alveoli
B. Proteinaceous exudate on alveolar septae
C. Bacterial overgrowth
D. Lymphocytic infiltration of alveolar septae
E. Neutrophilic infiltration of alveolar airspaces

Answer for Question 153

Answer: E (Neutrophilic infiltration of alveolar airspaces)

Explanation: The presenting symptoms are consistent with a community-acquired pneumonia, and the physical examination and chest x-ray are consistent with a lobar pneumonia, which is most commonly caused by Streptococcus pneumoniae. Although atelectasis, hyaline membranes, and bacterial overgrowth could/would all be present to some degree, the cause for the consolidation of the lung tissue (i.e., the lung tissue having a more solid appearance) is due to the neutrophilic infiltrate in the alveolar airspaces, filling the airspaces in the lung. Lymphocytic infiltration of the alveolar septae would be characteristic of a viral infection.

Question 154

A 34-year-old male presents to an acute care clinic with complaints of a productive cough and fever to 38.4 degrees Celsius for the past 3 days, associated with shaking chills and some chest pain when he breaths. Physical examination reveals dullness to percussion on the left side of the chest. Crackles and a pleural rub are also heard at this location. A chest x-ray reveals consolidation of the left lung. Of the following, if untreated, which complication is he most likely to develop?

A. Bronchogenic carcinoma
B. Amyloidosis
C. Fibrosis in the left pleural cavity
D. Alzheimer disease
E. Aortic dissection

Answer for Question 154

Answer: C (Fibrosis in the left pleural cavity)

Explanation: Given the clinical presentation, a bacterial lobar pneumonia is likely. The pleural friction rub would indicate that there is pleuritis. With a bacterial infection causing pleuritis, complete resolution would be less likely, and scar formation would occur. Bacterial (and viral) pneumonias are not a significant risk factor for the other disease processes listed.

Question 155

A 26-year-old male presents to the hospital with complaints of difficulty breathing, which has severely worsened over the past day. In the five days prior, he has had a fever, productive cough, and chills. In addition, his chest has hurt when he breathed in and with exertion he was short of breath. His friends told him to come to the emergency room two days ago, but he thought that he could wait it out. He has a temperature of 101 degrees Fahrenheit, heart rate of 108 bpm, blood pressure of 105/71 mmHg, and respiratory rate of 28 breaths per minute. Physical examination reveals dullness to percussion on the left side of the chest, accompanied by decreased breath sounds, and an absence of tactile fremitus. Of the following, what is the most likely diagnosis?

A. Pulmonary thromboembolus
B. Congestive heart failure associated with bicuspid aortic valve
C. Tension pneumothorax due to ruptured bleb
D. Empyema
E. Aspiration pneumonia with abscess formation

Answer for Question 155

Answer: D (Empyema)

Explanation: The clinical presentation is consistent with a community acquired pneumonia. The dullness to percussion on the left side of the chest combined with the decreased breath sounds and absence of tactile fremitus are consistent with an empyema. While the pneumonia alone could cause the dullness to percussion associated with the consolidation of the lobe, there would not be decreased breath sounds, and there would be tactile fremitus. While a pulmonary thromboembolus could, with infarction, lead to dullness to percussion, it would not produce the other physical examination findings, and is not associated with a productive cough. Congestive heart failure due to a bicuspid aortic valve would present much later in life, and would not be associated with the productive cough The individual has no described risk factors for aspiration pneumonia.

Questions 150-152: Lung pathology

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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