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Summary usmle u world question bank for usmle step 1 exams
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set 6 pathology wuestion bank for usmle step 1 exams
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USMLE STEP 1 PATHOLOGY QUESTION BANK 3
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1. Autopsy is performed on a 64-year-old male who di'ed ofrespiratory failure while hospitalized. Examination of his bronchi
reveals thickened bronchial w alls, neutrophilic infiltrates, mucous
gland enlargement and patchy squamous metaplasia of bronchial
mucosa. Whiclh of the following factors was likely the greatest
contributor to this patient's condition?
A. Environmental
B. Genetic
C. Allergic
D. Infectious
E. Neoplastic
Answer: A
Explanation:
The description of this patient's bronchial w alls is c·1assic for chronic
bronchitis. The leading cause of chronic bronchitis is cigarette smoking.
Chronic irritation by other inhaled environmental substances, such as air
pollutants and grain, cotton, or silica dusts, may also be a contributing
factor.
(ChoiceB)Geneticfactorsarenotknowntostronglypredisposetothedevelop
mentofchronicbronchitis.
(Choice C) Chronic asthmatics with extrinsic allergic asthma can
develop bronchial wall pathology (remodeling) which includes thickening
of the bronchial epithelium, basement membrane, and bronchial walls as
well as edema, inflammatory infiltrates, submucosal mucous gland
enlargement, and bronchial smooth muscle hypertrophy. However, the
infiltrate will consist predominantly of eosinophils and mast cells.
Furthermore, while asthma can cause chronic bronchitis (e.g. chronic
asthmatic bronchitis, chronic eosinophilic bronchitis), cigarette smoking
is a much more common cause.
,(Choice D) Repeated bronchial/bronchiolar bacterial and viral infections
can contribute to the development of chronic bronchitis, although to a
less significant degree than cigarette smoking. Acutely, infection can
exacerbate airway narrowing via mucus plugging and mural
inflammation. Chronic infection promotes reactive fibrosis. Cigarette
smoke predisposes to infection by impairing ciliary clearance and directly
damaging the respiratory epithelium. It also inhibits clearance of bacteria
by bronchial (and alveolar) leukocytes.
(Choice E) While chronic bronchitis can result in dysplasia of the
respiratory epithelium, potentially promoting neoplastic transformation of
epithelial cells, the reverse (that neoplastic transformation contributes to
chronic bronchitis) is not true.
2. Chest x-ray of a 64-year-old Caucasian male reveals the incidental
finding of pleural thickening and calcifications along the lower lung fields
and diaphragm. There is also a small right-sided pleural effusion. This
patient most likely has a history of exposure to:
A. Silica
B. Asbestos
C. Beryllium
D. Coal dust
E. Organic dust
F. Nitrous oxide
Answer; B
Explanation:
Localized pleural thickening w ith calcification, particularly of the parietal
pleura of the posterolateral mid-lung
,zonesanddiaphragm,isahallmarkofasbestosis.
Thesecalcifiedlesionsarereferredtoaspleuralplaques. Lung injury due to
asbestos inhalation predominantly affects the low er pulmonary zones
and manifests radiographically as linear interstitial densities in the lower
lobes. Small pleural effusions which are exudative and possibly blood
stained may occasionally be noted.
(Choice A) Unlike asbestosis, pulmonary silicosis is not strongly
associated with pleural plaques or effusions. Nodular densities and
eggshell calcifications of the hilar nodes are seen.
(Choice C) Pulmonary berylliosis closely resembles sarcoidosis
(nodular infiltrates, enlarged lymph nodes, non-caseating granulomas)
but is not strongly associated with pleural plaques or effusions.
(Choice D) The coal macules of coal worker's pneumoconiosis are
seen radiologically as multiple discrete nodules (1-4 mm), most
prominent in the upper lung zones. Pleural plaques or effusions are not
typical.
(Choice E) Hypersensitivity pneumonitis due to inh.alation of organic
dusts tends to result in diffuse nodular interstitial infiltrates on chest x-
ray. Pleural plaques or effusions are not typical.
(Choice F) Nitrous oxide (N20 ) is used as an anesthetic gas and is
relatively non-toxic.
, 3. Fine needle aspiration of a pulmonary lesion in a 35-year-old
Caucasian female is performed. The specimen is cultured, and grows
several bacterial species, including Peptostreptococcus and
Fusobacterium. The factor most likely to predispose to this patient's
condition is:
A. intravenous drug use
B. penetrating chest trauma
C. seizure disorder
D. urinary infection
E. occult malignancy
F. mitral valve prolapse
Answer: C
Explanation:
Peptostreptococcus and Fusobacterium species are components of the
normal mouth flora. Patients experiencing decreased consciousness
(e.g. patients with a seizure disorder) may aspirate oropharyngeal
contents, causing a lung abscess. On chest x-ray, a lung abscess
appears as a cavitary lesion with an air-fluid level. Lung abscesses
arising as a complication of aspiration typically contain mixed flora, often
including these two species. Lung abscesses cause fever, weight loss,
cough and foul-smelling sputum. There may also be anorexia, malaise,
chest pain and clubbing.
Lung abscesses may develop by the following mechanisms:
1. Aspiration of oropharyngeal contents is the most common cause.
These abscesses often contain Fusobacterium, Peptostreptococcus and
Bacteroides species. Risk factors include all conditions associated with
loss of consciousness, such as alcoholism, seizure disorders, prolonged
anesthesia, and severe neurologic diseases. Aspiration-associated
abscesses are found in the dependent parts of the right lung.
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