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Old 05-31-2011
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Question Source of Infection after visiting "red light" district

About six weeks after a male 25yr old visits the red light district in New Orleans, and he develops a nonprupritic, maculopapular rash. The rash is generalized and includes hands, feet, and mucous membranes of the oral and anogenital areas. The rapid plasma reagin (RPR) test is negative at the standard dilution.

Which organism is the most likely cause of the infection:

a) Haemophilus ducreyi
b) Treponema pallidum
c) Treponema carateum
d) Chlamydia trachomatis
e) Neisseria gonorrhea
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Old 06-01-2011
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a) Haemophilus ducreyi -- Not a painful rash, so excluded.
b) Treponema pallidum -- 6 weeks, nonpruritic, secondary syphilis?
c) Treponema carateum
d) Chlamydia trachomatis -- Does not spread to hands / feet
e) Neisseria gonorrhea -- Does not spread to hands / feet

Answer is B) T. Pallidum, causing Secondary Syphilis
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Old 06-01-2011
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Default B

It is secondary syphilis, primary syphilis has chancres and adenopathy. But why is the RPR negative. RPR can be negative in primary syphilis but its almost always positive in secondary? correct me if I am wrong
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Old 06-01-2011
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Quote:
Originally Posted by mle guy View Post
It is secondary syphilis, primary syphilis has chancres and adenopathy. But why is the RPR negative. RPR can be negative in primary syphilis but its almost always positive in secondary? correct me if I am wrong
Yes that threw me off too, I was expecting VDRL aswell, but I guess that would make the question too easy?
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Old 06-01-2011
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Quote:
Originally Posted by patelMD View Post
Yes that threw me off too, I was expecting VDRL aswell, but I guess that would make the question too easy?
So is it a false-negative then, because FTA-ABS would surely be positive.
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Old 06-01-2011
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Originally Posted by mle guy View Post
So is it a false-negative then, because FTA-ABS would surely be positive.
I think so, unless we're wrong about the answer
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Old 06-01-2011
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yeah i too think T.pallidum.
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Old 06-01-2011
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Default Answer: B Treponema pallidum

You guys are all right! This patient has secondary syphilis caused by Treponema pallidum, given the description of the rash, it's distribution, and the time of it's appearance. The RPR test is negative because of what is called the prozone phenomenon. In the case of secondary syphilis, a high level of antibody may interfere with antigen-antibody complex formation and may be interpreted as negative.
The take away point is that the RPR can be negative in secondary syphilis, and you need to do a more sensitive test such as FTA-ABS or dark field microscopy.
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