June 21, 2010

MRCP 1 Question 1

A 38 year old farmer is seen with severe headache and fever. He has a history of a ten day cough with bloody sputum and showed consolidation on a chest x-ray for which he was given erythromycin by his physician. Physical examination was unremarkable except for bilateral inspiratory crackles and a lumbar puncture was performed. This demonstrated a highly pleomorphic coccobacillii with gram-negative cell wall.

These features are characteristic of:
a) Streptococcus pneumoniae
b) Bacteroides fragilis
c) Coxiella burnetii
d) Escherichia coli
e) Haemophilus influenzae



ANSWER
The correct answer is C

Explanation

Coxiella burnetii, the etiologic agent of Q fever, is a highly pleomorphic coccobacillus with a gram-negative cell wall.

There are three presentations of Q fever : atypical pneumonia, rapidly progressive pneumonia, and pneumonia as an incidental finding in a patient with a febrile illness. This last presentation is probably the most common form of Q fever pneumonia.

In Q fever due to Coxiella burnetii the physical examination of the chest is often unremarkable. The most common physical finding is inspiratory crackles. Patients with rapidly progressive pneumonia usually have the physical signs of pulmonary consolidation.

About 5% of patients have splenomegaly. Fever and severe headache suggest central nervous system infection, and lumbar puncture is often performed.

The rapidly progressive form of Q fever pneumonia mimics legionnaires' disease and the pneumonic form of tularemia, and indeed, all the causes of rapidly progressive pneumonia enter the differential diagnosis.

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