Sunday, January 13, 2008

6 - respiratory system mcqs - 26 to 30

Question 26

A 40-year-old previously healthy woman, a non-smoker, has had episodes of fever, non-productive cough, and dyspnea over the past 3 months. Her symptoms disappeared after a month's vacation, but reappeared when she returned home to take care of her canaries. On physical examination there are no abnormal findings. A chest radiograph shows fine diffuse and nodular infiltrates in all lung fields. Her disease is most likely to be produced via which of the following mechanisms?

A Mast cell degranulation

B Progressive interstitial fibrosis

C Antigen-antibody complex formation

D Langerhans cell proliferation

E Infection with Mycobacterium kansasii


(C) CORRECT. Birds make a lot of organic dust from their feathers. The result is an extrinsic allergic alveolitis. Getting away from the antigen (such as a vacation) will improve the situation. This is a form of type 3 hypersensitivity.

(A) Incorrect. Asthma produces bronchoconstriction for short periods of time. Infiltrates should not be present. Extrinsic asthma is a form of type 1 hypersensitivity reaction, with allergen attaching to IgE bound to mast cells.

(B) Incorrect. Interstitial fibrosis is a progressive process leading to restrictive lung disease. The course is not episodic.

(D) Incorrect. In adults, the most common form of Langerhans cell histiocytosis is eosinophilic granuloma of lung, a process that produces larger nodules and is not episodic.

(E) Incorrect. Tuberculosis in an adult is typically the reactivation or reinfection type with upper lobe granulomas. Pulmonary disease caused by M. kansasii resembles that caused by M. tuberculosis in most cases. The cell-mediated immune response to tuberculosis is a form of type 4 hypersensitivity.


Question 27

A 63-year-old woman has had increasing dyspnea for 5 years. On physical examination her lungs are hyper-resonant without dullness. Tactile vocal fremitus is slightly decreased over all lung fields. Scattered expiratory wheezes and inspiratory rhonchi are present without basal crackles. She has a chest radiograph that reveals increased lung volumes and flattening of the diaphragmatic leaves. Spirometry demonstrates an FEV1 that is decreased more than the FVC so that the FEV1/FVC ratio is less than 70% of normal. Which of the following inhaled substances, which increases the elaboration of neutrophil elastase, is most likely to cause her pulmonary disease?

A Chlorine

B Silica

C Carbon monoxide

D Nicotine

E Carbon


(D) CORRECT. She has findings of emphysema, and smoking is the most likely underlying cause. The nicotine in the cigarette smoke is chemotactic for neutrophils, and cigarette smoke activates the alternative complement pathway, releasing more mediators for neutrophil recruitment. Neutrophil elastase can damage the lung parenchyma. Though neutrophils are not numerous in the lung with emphysema, the cumulative effect of even small numbers of neutrophils over many years leads to the tissue damage.

(A) Incorrect. Exposure to toxic gases produces an acute pneumonitis with injury to epithelium and edema.

(B) Incorrect. Silica dust produces nodules that diminish lung volumes and lead to a restrictive lung disease.

(C) Incorrect. CO poisoning has no significant effect on the lung, but CO binds more avidly to hemoglobin and leads to hypoxia.

(E) Incorrect. Carbon dust leads to anthracosis, which is a benign process that virtually everyone on earth now develops. Large quantities of coal dust can produce progressive massive fibrosis, a restrictive lung disease.

Question 28

A 54-year-old man has had increasing dyspnea for the past 6 years, but no cough. On physical examination there is increased jugular venous distension. He is afebrile. A chest radiograph shows increased lucency in upper lung fields and increased lung volumes, with flattening of the diaphragmatic leaves. There are no infiltrates. The pulmonary arteries are enlarged and prominent bilaterally, and his right heart border is enlarged. Which of the following pathologic findings is most likely to be present in his main pulmonary arteries?

A Granulomatous vasculitis

B Organizing thromboemboli

C Medial dissection

D Atherosclerosis

E Aneurysm formation


(D) CORRECT. Cor pulmonale is the result of pulmonary hypertension, which is the major cause for pulmonary atherosclerosis. His emphysema has reduced the pulmonary vascular bed, promoting the hypertension. Note that the forces driving systemic atherosclerosis are not operative on the pulmonary arterial system.

(A) Incorrect. Wegener granulomatosus is a process that can lead to pulmonary vasculitis, though the peripheral arteries are typically involved, and more of a restrictive lung disease develops.

(B) Incorrect. Pulmonary thromboembolism is an acute process. It is not related to emphysema.

(C) Incorrect. A dissection does not occur in pulmonary arteries, as in the aorta, because the pressures are not as high, even with pulmonary hypertension.

(E) Incorrect. Aneurysms may complicate atherosclerosis, but the degree of atherosclerosis and the arterial pressures in the pulmonary system are not as marked as in the aorta.


Question 29

A 44-year-old woman, a non-smoker, has had a fever and cough for the past 4 days. She does not have hemoptysis. She has not experienced weight loss, malaise, nausea, or vomiting. On physical examination her temperature is 37.6 C. There are decreased breath sounds over the right upper lung. A chest radiograph reveals a 6 cm area of infiltrates in the right upper lobe. She is given a course of antibiotic therapy, but her cough persists. A month later her chest x-ray now reveals a 3 cm peripheral mass in the right upper lobe. Which of the following neoplasms is most likely to be present in this woman?

A Squamous cell carcinoma

B Small cell anaplastic carcinoma

C Adenocarcinoma

D Mesothelioma

E Carcinoid tumor


(C) CORRECT. Peripheral lung cancers (adenocarcinoma and large cell carcinoma) show less of an association with smoking than central cancers (small cell and squamous cell carcinoma).

(A) Incorrect. Squamous cell carcinomas are often associated with smoking. They are often bulky central masses.

(B) Incorrect. Oat cell carcinomas have a close association with smoking. Such cancers are not common in nonsmokers. They often metastasize early, so that the primary site (usually in a central location) is small when discovered.

(D) Incorrect. Asbestos exposure is a likely antecedent to pleural mesothelioma, which produces a bulky pleural mass.

(E) Incorrect. Carcinoid tumors are neuroendocrine neoplasms on the opposite end of the spectrum from oat cell carcinomas. Carcinoids tend to form masses within the larger bronchi.


Question 30

A 70-year-old woman has been bedridden for 5 weeks following a cerebrovascular accident (CVA). She has the sudden onset of dyspnea, but has no further symptoms until two days later when she experiences left sided pleuritic chest pain. A day later she suffers another CVA and dies. At autopsy, she is found to have a wedge-shaped area of hemorrhage based on the pleura of the left lower lobe. Which of the following pathologic findings in her pulmonary arterial branches is she most likely to have?

A Atherosclerosis

B Aspergillosis

C Fat embolism

D Vasculitis

E Thromboembolism


(E) CORRECT. An embolus to a medium-sized arterial branch is not large enough to kill the patient, but large enough to cause an infarction. Her bedridden state predisposes her to deep venous thrombosis and thromboembolism--the CVAs are due to separate systemic arterial problems--or the systemic and pulmonary embolization can be tied together by a hypercoagulable state, or more remotely by a 'paradoxical' embolus through a patent foramen ovale once the right sided-pressures increased following the initial pulmonary thromboembolic event.

(A) Incorrect. Although they are part of the systemic circulation, they supply little blood to lungs. They are small and not involved with systemic atherosclerosis. Their lack of occlusion with thromboembolization leads to hemorrhage into pulmonary infarcts.

(B) Incorrect. Aspergillus fungal organisms like to invade blood vessels and can lead to thrombosis, but this infection is typically seen in immunocompromised patients.

(C) Incorrect. Fat embolism typically occurs following trauma. The microscopic emboli do not produce infarction.

(D) Incorrect. A vasculitic process such as Wegener granulomatosis would be diffuse, not localized. The size of the arteries involved with most vasculitides is too small to cause an infarction, but could lead to pulmonary hypertension, however.


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