So if we could do a podcast about rashes without the help of visual aids, then why not try to do our column the same way? Well, here goes.

No Visual Needed

The dermatologists remind us that purpura is the umbrella term for purple discoloration of the skin due to extravasated blood. These lesions don’t blanch. Petechiae are the small ones (less than 3 mm), while ecchymosis are the larger ones (greater than 5 mm.) With that in mind, the purpura flowchart only asks two questions: 1) Is the patient toxic/febrile? 2) Are the lesions palpable or non-palpable? This means that when it comes to pupura, there are only four conditions total: a toxic-appearing/febrile patient with either palpable (1) or non-palpable lesions (2) or a non-toxic-appearing/afebrile patient with either palpable (3) or non-palpable lesions (4). That’s it. The best part is you really don’t have to memorize the differential diagnosis of these four conditions. You simply have to know to assess the two questions when examining the patient during your encounter. Then you can pull out your PV card, and voilà, your afebrile well-appearing patient with palpable purpura very likely has autoimmune vasculitis.

We chose this particular example because the differential diagnosis for that branch of the decision tree conveniently has only one entry. What if that same patient had non-palpable purpura? The only possibility is idiopathic thrombocytopenic purpura (ITP). That means that if you have an overall well-appearing patient with non-blanching purple spots, you know it’s either autoimmune vasculitis or ITP. Now all you would need to do is touch the rash to decide which one it is. If you could feel the lesions, it would be ITP—not bad! The febrile/toxic branches have a few more options for the differential diagnosis, which is why you’ll want to have the PV card handy. The card also has similarly useful flowcharts for maculopapular, erythematous, and vesiculobullous rashes. The major branch points in these decision trees focus, again, on the sick versus not-sick distinction, as well location and distribution of the lesions and the presence or absence of Nikolsky sign. With just those few questions in mind, you can easily delineate an impressive number of rashes.

For more PV cards, check out ALIEM.com, and as always, you can download our recent episodes at FOAMcast.org or on iTunes. In addition to our show on “just in time” FOAMed resources, we’ve recently recorded shows covering news on intracranial hemorrhage management (spoiler: aggressive blood pressure control seems to be unnecessary; also transfusing platelets for spontaneous intracranial hemorrhage might be a bad thing after all), an entire show on the pericardium, and a show covering the various types of altitude-associated illnesses.