Derma Case: 12-year-old Girl with an Intensely Pruritic Rash

00:01 Our second case. Now, this is a 12-year-old tennis player.

00:05 Past medical history, again, of dermatitis -- pretty much anything that involves the skin from a lay audience is called dermatitis -- presents with an intensely pruritic rash on her arms over the last few days.

00:16 This is sounding again like atopic eczema. At baseline, she has intermittent flares of pruritic, erythematous papules overlying her antecubital fossa, volar wrists, bilateral ankles, for which she uses topical steroids. Slam dunk case of atopic eczema.

00:33 5 days ago, however, she had to go into the woods behind the practice courts to retrieve a tennis ball.

00:39 Allergic to tree nuts, eczema, atopy.

00:42 Father eyes allergic rhinitis, sister has asthma.

00:45 Review of systems, again, is negative. Boring vitals. Moving on to the skin exam.

00:50 Scattered erythematous papules and vesicles, and small bullae -- a little bit unusual for eczema -- oozing some yellowish adherent fluid with crusts.

01:02 And you can see the picture there. Looks like a kind of moist picture rather than a dry lichenified-type picture. In this case, again going to our differential diagnosis, seb derm doesn't happen on the arms.

01:15 Irritant contact dermatitis? screen the patient for other potential exposures Allergic contact dermatitis I think that would be our leading guess here because we're worried that since she was in the woods, we're worried about an exposure to urushiol. Again, that's the oil resin that comes from poison ivy. And this would be a classic presentation of that over the span of a few days.

01:38 And we can expect that some new crops may appear over the next couple days, simply because the skin may have been absorbing that urushiol at different rates. Doesn't look like psoriasis, none of the silvery scale, atypical location. And again, she clearly has atopic dermatitis, but this is an acute problem on a backdrop of some chronic skin disease. Final diagnosis is clearly an allergic contact dermatitis from urushiol.

02:04 Okay. Now we have a few quick review questions. I'll ask a question. Feel free to pause the screen, so you can reflect on the answer.

02:12 What do you remember about irritant and allergic contact dermatitis, and in particular, what distinguishes the 2 of them? All right. By way of review, let's take a look at this slide.

02:25 The key point here is the etiology. An allergic contact dermatitis is caused by a localized T cell-mediated response to an allergen, and it's a delayed-type hypersensitivity reaction, whereas irritant is a localized inflammatory response to a physical or a chemical irritant.

02:46 There's a direct cytotoxic response going on in that case.