Master the board step 3

Dermatology
Syphilis
Both primary and secondary syphilis present mainly with cutaneous disorders.
Primary Syphilis
The chancre of primary syphilis is an ulceration with heaped-up indurated
edges that is painless the majority of the time.
The best initial test is a darkfield examination. This is because there is a false
negative rate of 25 percent for both the VDRL and RPR. In other words, these
serologic tests need several weeks to become positive, and they are only 75
percent sensitive in primary syphilis.
Both primary and secondary syphilis are treated with a single intramuscular
dose of penicillin. In those patients allergic to penicillin, doxycycline orally
for 2 weeks is the alternative therapy.
Secondary Syphilis
Secondary syphilis presents with a generalized copper-colored, maculopapular
rash that is particularly intense on the palms and soles of the feet. The other
manifestations of secondary syphilis are predominantly dermatologic as well:
the mucous patch, alopecia areata, and condylomata lata.
The VDRL and RPR tests have nearly 100 percent sensitivity in secondary
syphilis.
As above, both primary and secondary syphilis are treated with a single intramuscular
dose of penicillin. In those patients allergic to penicillin, doxycycline
orally for 2 weeks is the alternative therapy.
Scabies and Pediculosis
Scabies
Scabies involves primarily the web spaces of the hands and feet but can also
cause pruritic lesions around the penis and breast. Itching can be extreme in
both cases. Because Sarcoptes scabiei is quite small, all that can be seen with the
naked eye are the burrows and excoriations around small pruritic vesicles.
Scabies often spares the head.
Immunocompromised patients, such as those with HIV, are particularly vulnerable
to an extremely exuberant form of scabies with severe crusting known
as “Norwegian scabies.”
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