Don't be RASH: Emergency Physician's Approach to the Undifferentiated Lesion

Don’t be RASH: Emergency Physician’s Approach to the Undifferentiated Lesion

By Genine Siciliano MD
Chief Resident, Emergency Medicine, UT Southwestern/Parkland Memorial Hospital

Edited by Alex Koyfman MD and Stephen Alerhand MD


You start your shift and your first patient is a 35-year-old male who presents with a mild fever, tachycardia, and what looks like the worst rash you have ever seen! His skin is diffusely erythematous, covering almost 95% of his body, with exfoliative plaques, and diffuse pustular lesions. Needless to say the patient is in severe pain. He then tells you this is his psoriasis and you are like ….WHAT?!

Psoriasis doesn’t look this bad. People with psoriasis don’t usually end up in the ICU… right?

I recently gave a senior Grand Rounds talk on dermatologic emergencies for my fellow residency class. I chose this topic because I feel it is one that the emergency medicine (EM) physician does not necessarily feel very comfortable discussing. Then I thought to myself, why is that? We love to talk about airway management, MI, sepsis, ACLS, and stroke, but we rarely talk about rashes. The EM dermatology literature is scarce and not much new information nor cutting-edge treatments exist for EM management of toxic rashes. Thus, my goal was to discuss how the EM physician should approach the unknown lesion. The EM physician is the one on the front lines. Thus, it is our job to quickly differentiate the benign from the lethal rash, subsequently providing basic resuscitation and involving the appropriate consultants in a timely fashion.

Rashes are responsible for over 5% of all ED visits. Thus, it is crucial for the EM physician to have a systematic, educated approach to his/her differential in order to recognize sick from not sick and initiate appropriate initial interventions.


When evaluating a patient in the ED with a new rash, there are three major questions to ask yourself:

  1. What is the overall morphology? When discussing morphology, it is important to distinguish between the primary and secondary lesion. Often we see the patient’s rash after it has undergone some secondary changes. The rash may have originally been maculopapular or vesicular but now appears excoriated and eroded, thus making its identification and diagnosis even more difficult for the emergency physician. Examples of common primary lesions include: papule, macule, nodule, plaque, pustule, vesicle, bulla, petechiae, purpura, scales. Examples of secondary lesions include: erosions, ulcers, excoriations, crusts, and atrophy.
  1. What is the overall pattern, distribution, and percentage of the body affected? This information is the next step in narrowing down the differential as well as distinguishing a benign from potentially lethal rash. Is it mostly peripheral or centrally located? Mostly extensor or flexor surface? What percentage of the body is affected? I think it is obvious to emphasize that the more extensive the body surface area involved, the more potentially lethal the rash could be. In our busy county ED, there is very little space and often very limited private rooms for a thorough skin exam. Regardless, this is not an excuse. For a patient with a potentially lethal rash, it is crucial to get the patient in a gown and examine the entire skin surface!
  1. Is the patient sick or not sick? How do we determine this? This is where we take into account the entire picture. We must take a complete history and ask about recent exposures, new medications, occupation, travel, tick bites, contacts with similar rashes, and past medical history to assess for more “at risk” populations (HIV, DM, other immunocompromised, alcoholics). Next, assess the patient’s vital signs. Subtle abnormalities can be the first hint of a potentially toxic rash. After an evaluation of a basic history and physical, your next step is to decide if there are any other red flags. What are some red flags for a potentially toxic rash? These include extremes of age, adenopathy, severe pain, arthralgias, hypotension, high fever, extensive skin involvement (anything over 10% BSA should probably concern you), rapidly progressive, mucosal involvement (this is never good), positive Nikolsky sign, petechial or purpuric morphology, and specific lab abnormalities. Speaking of lab abnormalities, what would you be looking for? Many potentially lethal rashes cause similar lab abnormalities. These can be hematologic (leukocytosis, atypical lymphocytes, eosinophilia, anemia, thrombocytopenia, coagulation abnormalities), as well as severe electrolyte and liver enzyme abnormalities. It is usually a good idea to obtain blood cultures on these patients, and in the toxic rash you will likely be starting empiric broad-spectrum antibiotic therapy. Other specific serology studies, scrapings, and biopsies can be saved for admission and our dermatology consultants.

So how do we put it all together? The Modified Lynch Algorithm

Prior to my lecture I had never heard of this algorithm. At one can find a practice bulletin from 2002 by Drs. Nguyen and Freedman that identifies a modified lynch algorithm for the EM approach to the unknown lesion. It is a great tool that the EM physician (especially the novice EM physician) can use to categorize the unknown lesion and develop an appropriate and complete differential diagnosis.

This algorithm categorizes a potentially lethal rash into 6 major categories based primarily on morphology: (1) maculopapular, (2) diffuse erythematous, (3) non-erythematous, (4) petechial/purpuric, (5) pustular, (6) vesiculobullous. Once you have decided which of these 6 categories your lesion fits into, you can further narrow your differential based on the pattern/distribution and whether the patient is sick versus not sick.

As an EM physician, it is difficult to have working knowledge of the hundreds of different types of rashes that exist. However, I argue that it is not the job of the EM physician to diagnose every rash that comes in the ED. That is the job of the dermatologist who has the luxury of time and biopsies. Rather, it is our duty, just like chest pain and syncope, to rule out the life-threatening causes of skin lesions, quickly identify a potentially lethal rash, and provide the appropriate initial stabilization, resuscitation and disposition (ICU, surgery).

This algorithm is a great way to organize and ensure a more complete differential when evaluating a potentially lethal rash. One thing to note is that this algorithm is not comprehensive, but it is a great starting point and often all the EM physician needs to determine the appropriate disposition for the patient. Lastly, it is also important to note that many toxic rashes overlap categories (i.e. DRESS Syndrome can be maculopapular, diffusely erythematous, or even petechial!). Thus, the point is, if it looks bad and has some red flags, admit the patient, provide supportive care and antibiotics if indicated, consult your dermatology, ICU, and possibly surgical colleagues and figure out the exact diagnosis later.

A note on topical steroids

As you know, most of the rashes we see in the emergency department are benign and often treated with topical steroids. How do we dose topical steroids? How much and for how long should we prescribe them? What about oral steroids? There are just a few things to keep in mind when sending someone home with topical steroids. First, pick the appropriate strength. Low dose for the face and genitals (i.e. 1% hydrocortisone) and medium potency for the rest of the body (i.e. 0.1% triamcinolone). How much? This is often the hardest question in the ED. An easy way to remember is “45, 90, 180.” 45g is often enough for 2 weeks of topical treatment of the face or arms, 90 for an extensive percentage of the legs, and 180 for the trunk. For more information there are formulas that you can use for more exact dosing described in Tintinalli’s dermatology chapter. Typically you should prescribe enough for 2-3 weeks of topical therapy. Regarding oral steroids there is some controversy over the length of time and when oral steroids are indicated. In general, one should consider oral steroids in refractory cases that are not improving with topicals and those that cover a significant body surface area. There is some controversy regarding how long to treat with oral steroids. In the emergency department we love short 4-5 day bursts of steroids. However with rashes this can be dangerous as there is the potential risk of a rebound dermatitis. Our dermatology colleagues thus recommend treating with a 2-week taper. Although there are no randomized controls trials or other substantial literature to support this practice, it makes sense to treat with a longer course with extensive skin lesions. Further research is needed in this area.

ED Management and Disposition

Once you have determined the patient is sick and needs ICU level of care, there are several things you need to consider doing prior to transport.

  1. Withdraw the offending agent. This is a critical first step.
  2. Electrolyte management/fluids. Severe rashes can cause serious disruptions in fluid balance, thermoregulation, infection control, and electrolytes.
  3. Antipyretics and pain control as indicated.
  4. Sepsis management. Patients often need to be started on initial broad-spectrum antibiotics later tailored to the etiology identified. If the likely etiology is more obvious (i.e. meningococcemia), you can narrow your initial antibiotic approach to the likely diagnosis.
  5. Involve appropriate consultants EARLY, especially surgery. Remember that necrotizing soft tissue infections can have very subtle skin findings initially. If there is any suspicion (i.e. recent trauma to extremity with new infection, crepitus or gas, history of diabetes) get your surgeon involved early and start antibiotics.
  6. Defer systemic steroids to your consultants. Some toxic rashes have been shown to significantly improve with steroids and reduce mortality (i.e. pemphigus vulgaris) while others can worsen (i.e. controversial in SJS/TEN). Thus, try not to initiate systemic steroids without the help of your dermatologic and ICU teams.
  7. Admit to ICU/burn unit. This is often the only setting in which a patient can have appropriate close monitoring, serial skin exams, and complex wound care.

So back to our case…The patient was found to have generalized pustular psoriasis. This is a rare form of psoriasis in which most or almost all the skin surface is involved with scaly, erythematous, pus-filled blisters and plaques. It is immune-mediated and a patient does not necessarily need to have a history of psoriasis to develop such a syndrome. It can often be triggered by infection, stress, medications, or steroids. Patients often present febrile, in severe pain, and very ill. This lethal rash can cause anywhere from an 8-20% mortality. These patients are often treated similar to burn patients with very complex wound care and careful attention to appropriate fluid and electrolyte repletion and treatment of any secondary infections. These patients can die from infections and metabolic complications.

In summary, it is the job of the EM physician to have an organized, systemic approach to the unknown lesion. We must quickly recognize toxic from benign rashes, and initiate appropriate initial resuscitative measures. The modified lynch algorithm is a useful tool and resource to help organize our differential as young EM physicians and initiate appropriate interventions. Lastly, get your consultants involved early, and advocate for ICU level of care for better observation and wound care.



– Nguyen T., Freedman J. Emergency Medicine Practice Bulletin. Dermatologic Emergencies: Diagnosing and Managing Life-Threatening Rashes. September 2002. Vol 4, No. 9.
– Tintinalli’s Emergency Medicine. 7th Edition.

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