Urticaria

I'll keep this short and sweet:  If you want to distinguish between urticaria and urticarial vasculitis, either ask the patient if the lesions last more than 24 hours, or have them come in after having drawn a border around the urticarial lesion, much the same as if you were documenting cellulitic change.  As one of our playas noted, you can also look for petichiae or bruise-like change to sniff out UV, but the easiest way is simply to ask the patient how long they last.

Rocky Mountain Spotted Fever

Rocky Mountain Spotted Fever is a rickettsial disease caused by Rickettsia rickettsii, and the natural history of RMSF goes like this:  1-2 weeks after being bitten by a tick from the Ixodid ticks, primary among them are the wood ticks (Dermacentor andersoni) and dog tick (D. variabilis), the victim develops constitutional symptoms (fever, chills, malaise) and a centripetal rash that begins on the distal extremities and marches inward toward the trunk.  This time lapse from the onset of the rash to the truncal manifestations can be as short as 6 hours.  Over the next couple of days, the rash becomes petichial and hemorrhagic, and if the patient isn't treated by day 5, the fatality rate rapidly climbs.  Problem is, in up to 20% of cases, there is no rash.  The usual cause of death is acute renal failure. If treated in time with a tetracycline derivative or chloramphenicol, the death rate is nil. 

About four years ago, I  had the pleasure of having a different rickettsial disease, R. conorii being the causative organism (bonus: which disease did I have and where did I get it?) and I thought someone was jackhammering the inside of my skull for about a week, in spite of starting Doxy as soon as I figured it out.  Not fun.  

Lupus pernio (Sarcoidosis)

First off, this is a testmanship question.  I just discussed unknown rashes, etc. on African American patients being sarcoidosis until proven otherwise, and then I throw out an image of strange papules on the nose, and- imagine that!- he's African American.  You could win lots o' dough in Vegas if you were to hit the tables with these kinds of odds in your favor.  

Lupus pernio is characteristically violaceous to skin colored, smooth shiny papules and plaques around the nose, cheeks and lips.  It is associated in nearly 75% of cases with chronic fibrotic respiratory tract involvement, so the correct diagnosis is important to the patients because the correct treatment can interrupt a cycle of disease that may cripple or rarely kill the patient.  Lupus pernio is associated with other manifestations of sarcoidosis, including bony involvement, but the primary risk is the association of the pulmonary tree.  

For those of you who got it right, reward yourself by clicking this link:  http://www.youtube.com/watch?v=9bZkp7q19f0

If you missed it, click this link:  http://www.youtube.com/watch?v=pWS8Mg-JWSg

Sarcoidosis

This is a pattern-recognition question.  If you take away the patterned aspect of this Q, you end up with a laundry list of ddxes: everything from infectious (deep fungal, AFB, bacterial, parasitic, viral) to neoplastic (weird CTCLs, etc.) to factitial (excoriated bug bites, etc) to inflammatory.  This is, of course, a special kind of inflammatory condition, and one that is all too common in African Americans.

From now on, for the rest of your natural lives, please remember this:  Any weird rash on African Americans can be sarcoidosis, and the importance of this point is this:  In many cases the skin manifestations of sarcoidosis precedes the other symptoms, and as such is the bellwether for the disease.  The worse the skin disease, the worse the systemic sarcoidosis.  And since we are often tempted to treat inflammatory skin diseases empirically, we can miss an important cutaneous manifestation of a systemic disease.  Given that sarcoidosis can irreversibly damage kidneys, eyes, lungs and liver, it is well worth recognizing the possibility and diagnosing it before the cat, so to speak, gets out of the bag.

Sarcoidosis, like syphilis, is a great imitator.  It can look like many different diseases (see the first paragraph above) and can cause great harm, like lues, if left unrecognized. 

Sarcoidosis is more common in the African American community at large (three times as common as the general population) and is more severe than in Caucasians.  So, in the future, if I throw up an image, and it is from an African American, and you can't tell exactly what it is, your answer should be "sarcoidosis until proven otherwise".

Allergic Contact Dermatitis to Gear Shift Knob (Australia)

This was, no doubt, a challenging question.  The problem with trying to piece together a story for a guy with a localized contact derm on the hand is that you need some history to pull everything together.  If you practice is like ours, most of the time the patient does not present to your office with a known allergen in mind, because if they did, they wouldn't be bothering you with a mystery they've already solved.

In this case, I wanted you to put it all together.  Your clues were what you see above, which is a clear case of localized allergic contact dermatitis.  Second, I gave you some clues:  1) He was a skin cancer patient  2) It was a localized dermatitis secondary to rubber.  At this point (as one of you did) you should be thinking "why did he say skin cancer patient?" and put together that it had to be in a latitude conducive to skin cancer.  But wait!  There's more!  Why the localization to the left hand?  Gotta be an answer.  That was when our Sherlock figured out that in some countries that were formerly part of the British Empire (or influenced by them as in the Japanese) they drive with the shifter on the left, not on the right.  The British Isles are not known for their skin cancer problems, so it had to be either Australia,  or New Zealand.  Playing the odds, since Australia is much bigger than New Zealand, the answer was Australia.  

Australia has a very highly developed derm community, and first among the superstars of Aussie derm is Robin Marks. For a bonus point, what does "Slip, Slap, Slop" mean? Dr. Marks has developed a body of literature which has informed the rest of us on such subjects as which side of the body has more AKs and what is the likelihood an individual AK will turn malignant.  Not bad for a country founded as a penal colony...

Behcet's Disease

Behcet's is a pretty interesting syndrome, in that it affects widely separated parts of the body, and tends to be pretty serious.  Also known as Oculo-Oral-Genital Syndrome, it consists of recurrent aphthous oral ulcers at least three times in twelve months, in conjunction withany two of the following:  retial vasculitis or uveitis, cutaneous lesions such as erythema nodosum, pseudofolliculitis or papulopustular lesions (think lesions similar to fire ant bites), a positive result of a pathergy test or recurrent genital ulceration.  A positive pathergy test is the stimulation of the formation of similar lesions by scratching or puncturing the skin.

The proper way to pronounce Behcet's is Beh-Chets, NOT Beh-shet's.  I would have allowed Beh-Jet's, since the ch sound in Turkish is similar to a j, but nobody answered that way.  

Tuberous Tendinous Xanthomas

Well, this is a repeat question (from May 16th) and so I will direct you to that discussion, but the most important aspect of this question is that many of you got it right.  Please think in terms of depositions into the skin, and then run your differential dx based upon location, appearance and peripheral clues.  You all nailed the elevated lipids, so nice job overall.  By the way, this was repeated in error, and I apologize for not making it a harder Q.