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<< Dermatologic Emergencies: Diagnosing And Managing Life-Threatening Rashes

Emergency Department Evaluation

Triage/Initial Nursing Interventions

The triage nurse should rapidly identify those patients with a rash who appear seriously ill or likely to  decompensate. High-risk patients include those with abnormal vital signs, altered mental status, or potential airway compromise. A petechial rash should also prompt early physician involvement, especially when accompanied by fever or confusion. In some hospitals, patients with fever and a rash are placed in respiratory isolation, especially if the patient is immunocompromised. The triage nurse should ensure early isolation of patients with lesions compatible with chickenpox or meningococcemia. All toxic-appearing patients with a rash require IV access, an ECG, and pulse oximetry monitoring. Oxygenation, perfusion, and a bedside blood sugar must be assessed in all patients with altered mental status.

Red Flags

Look for the following "red flags" when evaluating a patient with an unknown rash, as these may indicate serious illness. (See Table 3.) Fever suggests that an infectious or inflammatory process may be present. Infants and the elderly are more prone to infections due to a decrease in their immune status. While most patients with rash and fever have a benign viral exanthem, fever will also accompany lethal conditions such as Rocky Mountain spotted fever and meningococcemia. Other causes of fever include malignancy and certain medications.

Petechiae or purpura can be seen in some benign conditions; however, their presence should "raise the antennae" of the emergency physician.

Lesions of the oral or genital mucosa, as seen in Stevens-Johnson syndrome, may suggest that a severe systemic process is present, usually due to drugs or an infectious process.

Altered mental status or confusion should alert the emergency physician to the possibility of sepsis, hypoperfusion, and central nervous system involvement, as seen in meningococcemia.

Most rashes are not significantly painful, nor are they exquisitely tender to the touch. Patients who have pain out of proportion to tenderness of an extremity may have necrotizing fasciitis. (Necrotizing fasciitis is discussed in further detail in the January 2001 issue of Emergency Medicine Practice, "Skin And Soft-Tissue Infections: The Common, The Rare, And The Deadly.")


Gathering data about the character and progression of the rash, along with other key elements of the patient history, is essential to detect life-threatening rashes. The following key questions should be a part of every patient history:

  1. When did the rash appear, and how quickly did it progress? The most lethal rashes often progress rapidly. Acute urticaria with anaphylaxis can start within minutes after contact with the inciting agent. (See the April 2000 issue of Emergency Medicine Practice, "Allergic Emergencies And Anaphylaxis: How To Avoid Getting Stung.") The petechial rash of Rocky Mountain spotted fever generally occurs four days after exposure but will then spread swiftly.7 In meningococcemia, the rash can progress over hours. A non-allergic drug-induced rash can take days or weeks to evolve.8
  2. Did the rash change over time? Certain rashes change their morphology over time. For example, the lesion of anthrax begins as a pruritic papule that then forms an ulcer over 24-48 hours, finally becoming a black eschar after seven days. (See the July 2002 issue of Emergency Medicine Practice, "Bioterrorism And The Emergency Physician: On The Front Lines.")
  3. What was the progression of the rash? Where did the rash start? Vasculitic rashes generally spread in a peripheral-to-central pattern, whereas viral rashes (e.g., varicella) start centrally and spread peripherally. 9 A localized rash that does not progress may mean a contact dermatitis depending on the situation (e.g., dermatitis on both hands after wearing latex gloves).
  4. Is the lesion pruritic? Itching is probably a primitive form of pain, mediated by histamine released by mast cells. Other mediators of itch include opioid peptides, prostaglandins, and tachykinins. Diffuse pruritus without a rash can be seen in biliary cirrhosis or certain cancers, especially lymphomas. Pruritus with a diffuse rash may be from an acute allergic reaction or other inciting agents, such as dermatitis herpetiformis from gluten sensitivity. Scabies and poison ivy, in particular, usually present with a profound itch, although the most common reason for pruritus is xerosis (dry skin).10
  5.  Has there been any recent travel? Travel to certain geographical regions may expose the patient to organisms not typically seen in your ED. For example, a petechial rash in someone who has been to a wooded area may be Rocky Mountain spotted fever or ehrlichiosis. Lyme disease is endemic in the Northeast, mid-Atlantic, north Central, and far West regions of the United States.11 Consider typhus if there is a history of flea bites, travel to the southwestern United States, and a maculopapular rash that spreads from the trunk to the extremities. Hemorrhagic fevers present with a maculopapular rash and recent travel; dengue fever is endemic to parts of the Caribbean, while Ebola is found in sub- Saharan Africa.
  6. What is the patient's past medical history? A person's medical history may predispose him or her to certain dermatologic findings. For example, patients with an artificial heart valve, cardiac valvular lesions, or IV drug use may have endocarditis. Certain cutaneous conditions tend to recur in the same patient, such as herpes zoster associated with HIV or recurrent erythema multiforme following herpes simplex or mycoplasma infections. Inquire about the patient's immune status. Anasplenic or immunocompromised patient is susceptible to encapsulated organisms such as meningococcemia. HIV disease and chemotherapy predispose to thrombotic thrombocytopenic purpura, while those who are diabetic, debilitated, or alcoholic are vulnerable to necrotizing fasciitis.
  7. What is the patient's occupation? Daycare workers, college students, and military personnel are susceptible to outbreaks of meningococcemia, while postal workers or healthcare professionals may be exposed to anthrax. Consider tularemia in a game trapper who presents with regional adenopathy, an ulcerated lesion, and flu symptoms.
  8. What medications is the patient taking? Cutaneous drug reactions occur in about 2%-3% of hospitalized patients and 1% of outpatients.12 While most reactions are benign maculopapular or fixed eruptions, life-threatening presentations may occur. Such potentially lethal conditions include Stevens- Johnson syndrome and toxic epidermal necrolysis. Immediate life-threatening drug reactions include anaphylaxis and angioedema, both of which can compromise the airway.13
Determine whether the patient used any creams or medications that may have altered the morphology of the rash. Diphenhydramine or topical corticosteroids may decrease the erythema or urticaria of a histamine mediated rash.

Physical Examination

Perform the physical examination in a systematic fashion from head to toe, paying special attention to abnormal vital signs. When evaluating a rash, the "get naked" policy should be enforced (for the patient). Patients often remain blissfully unaware of a rash on their back, buttocks, perineum, or soles. Look carefully for involvement of the mucous membranes (mouth, lips, conjunctiva, anus, and vagina). Adequate exposure and good lighting are important when looking at a rash; natural light or white light is recommended. Touch the rash (with gloved hands, as lesions of secondary syphilis are contagious and no one knows how far scabies can jump). Press on lesions to see whether they blanch to better diagnose petechiae. Rub erythematous skin to see if it sloughs. This result, known as Nikolsky's sign, signifies a potentially life-threatening diagnosis such as toxic epidermal necrolysis.

The goal of the physical examination is not necessarily an instant diagnosis. In many cases, it is enough to detect toxicity and categorize the rash so that it can be identified with the aid of books or a consultant.

General Appearance And Vital Signs

Before closely examining the rash, assess the general appearance of the patient. Abnormal vital signs or evidence of toxicity should prompt interventions and accelerate the evaluation.

Head-To-Toe Examination
  • Head: Look at the patient's scalp, conjunctiva, and oral mucosa. Oral ulcers or blisters imply a serious systemic reaction, as seen, for example, in Stevens- Johnson syndrome or pemphigus vulgaris. The presence of oral thrush suggests HIV-related disease (although it can be seen in patients with uncontrolled diabetes and those who have recently completed a course of antibiotics). Conjunctival injection is found in Kawasaki disease and viral syndromes. When endocarditis is a possibility, a funduscopic exam may reveal Roth's spots, which appear as white-centered etinal hemorrhages.
  • Neck: In the ill-appearing patient, check for nuchal rigidity and other meningeal signs. In potential cases of anaphylaxis, look for signs of airway compromise, such as stridor, drooling, or laryngeal swelling.
  • Lymph nodes: Adenopathy is a nonspecific finding seen with drug reactions such as serum sickness and hypersensitivity syndrome. Adenopathy may be associated with infections, including viral, bacterial, rickettsial, and spirochetal disease. Mononucleosis is a common cause of generalized adenopathy. The acute retroviral syndrome that occurs with the initial infection of HIV presents as a "mono-like" illness with diffuse rash and generalized lymphadenopathy. Look for regional lymphadenopathy as well. Patients with Kawasaki disease usually demonstrate cervical lymphadenopathy, with at least one lymph node measuring 1.5 cm or more in diameter. Postauricular nodes accompany adenovirus infection. In addition to the cervical nodes, evaluate for adenopathy proximal to an extremity lesion. The axillary nodes are often swollen in cutaneous anthrax of the upper extremity.
  • Lung: Observe for signs of bronchial constriction and edema, such as tachypnea, wheezing, and retractions that may accompany acute allergic reactions or early sepsis.
  • Cardiovascular: While most heart murmurs are either functional or benign, they may be associated with endocarditis—especially in the setting of IV drug abuse.
  • Abdominal: Palpate for hepatosplenomegaly, which can occur with drug hypersensitivity or viral illness. Non-surgical diffuse abdominal pain may occur with allergic angioedema, while dull right upper quadrant pain suggests a hepatitis-related rash. Look for a laparotomy scar. If present, ask the patient, "Are you sure you still have your spleen?"
  • Trunk and chest: Most viral exanthems start on the trunk and then spread to the extremities (centrifugal spread). These rashes are fine, macular papular erythematous eruptions that usually become confluent. Drug allergies usually begin on the trunk as discrete macules/papules, which spare the face, and then spread to the extremities. Bullous lesions in a dermatomal pattern are likely to be herpes zoster. Fine, scaling, faint pink papules in a "Christmas tree" pattern in the trunk may be pityriasis rosea, especially if accompanied by a "herald patch." This oval lesion marks the first appearance of pityriasis rosea and is usually found on the trunk. It measures 1-2 cm in diameter and has central pink area, sometimes lined with small scales, surrounded by a darker peripheral zone.
  • Genital: Look in the mucosal areas of the anus and scrotum or vulva for target lesions and bullous lesions characteristic of erythema multiforme or Stevens-Johnson syndrome. Tinea cruris and erythrasma are also found in the genitocrural area. Both conditions present with a finely wrinkled, scaly rash that is reddish-brown in color. When erythrasma is viewed under a Wood's lamp, it fluoresces a bright coral red. Diffuse tender erythema around the scrotal and perineal areas (especially if associated with subcutaneous air) may represent Fournier's gangrene. (See the November 2000 issue of Emergency Medicine Practice, "Male Genitourinary Emergencies: Preserving Fertility And Providing Relief.")
  • Extremities: Palpable purpura and petechiae usually present in the extremities, especially around the ankles and wrists. The petechial rash of Rocky Mountain spotted fever spreads from the wrists and ankles toward the body (centripetal spread). Pain out of proportion to tenderness is found with necrotizing fasciitis; in this case, the affected limb may become tense with shiny erythema. (See the January 2001 issue of Emergency Medicine Practice, "Skin And Soft-Tissue Infections: The Common, The Rare, And The Deadly.") Sparse hemorrhagic pustules about the hands and feet imply gonococcemia.
  • Joints: Arthralgias are thought to be the result of antibody-antigen deposits in joints and may be a sign of serum sickness. Arthralgias with a rash are seen in Rocky Mountain spotted fever, drug reactions, and bacterial and viral illnesses. Disseminated gonococcal infection may present with frank arthritis and a meager hemorrhagic-pustular rash. 
  • Palms and soles: Involvement of the palms and soles usually signifies inflammation of the small vessels and can be drug-induced or pathogen-induced.8 The classic target lesions of erythema multiforme are often found on the palms and soles. The "nickel and dime" lesions of secondary syphilis are similarly prominent in these areas. In secondary syphilis, these symmetric lesions begin as faint papulosquamous macules that darken over time. In toxic epidermal necrolysis, Kawasaki disease, scarlet fever, and toxic shock syndrome, there is late desquamation of the hands and feet. However, since desquamation usually occurs 7-10 days after the acute illness, this finding is usually not helpful in the ED.
  • Nails and fingers: These areas provide important clues to the diagnosis of endocarditis. Splinter hemorrhages are found under the nails, while Osler's nodes are pea-sized subcutaneous nodules in the pulp of the fingers or toes. Janeway lesions are nontender erythematous, hemorrhagic macules on the palmar aspect of the fingers.
"I'm tired of all this nonsense about beauty being only skin-deep….
What do you want—an adorable pancreas?"
—Jean Kerr

The Skin Examination

First, the clinician should get an overall view of the rash, and then the primary lesion can be closely examined. A magnifying glass may be helpful when looking at a single lesion. The lesion should be palpated with a gloved finger to assess its texture and to see if the lesion blanches. If it is unclear whether a lesion blanches, use a glass slide to compress the area.

The following four major skin signs should be noted during the evaluation of any skin lesion or rash:14

  1. Type of lesion: This description should be for the representative lesion, as described in Table 1. Note if there are any secondary changes or if there are scaling, crusts, or fissures, as described in Table 2. Determine the color of the lesion and assess for erythema, desquamation, and tenderness.
  2. Shape of the individual lesion: Is the lesion round, oval, annular (ringed-shaped as in anthrax), iris-shaped (as in erythema multiforme), umbilicated (molluscum), or irregular (petechial)? 
  3. Arrangement of multiple lesions: Are the lesions isolated, grouped (linear, annular, serpiginous), or disseminated (scattered discrete lesions, or diffuse involvement as in viral exanthem or drug allergy)? Linear patterns not in a dermatomal distribution usually signify contact dermatitis (e.g., poison ivy) and, when located in the finger web spaces, scabies. A scattered, diffuse macular rash suggests a drug allergy.
  4. Pattern of the rash: Pattern is the functional/physiologic arrangement of the lesion, such as sunexposed area, flexor/extensor surface, or hairbearing areas. Also, note if the distribution is symmetrical or unilateral. Bilateral symmetry usually signifies a systemic internal event, whereas isolated lesions indicate a local process such as contact dermatitis. A rash in a sun-exposed distribution is compatible with a photosensitive drug reaction (e.g., tetracycline).
General Diagnostic Testing

Blood Tests

There are few studies that provide an evidence-based approach to laboratory testing in patients with a rash. Furthermore, with the exception of secondary syphilis, blood tests will almost never supply the etiology of a rash in the ED. In patients who are not toxic or febrile, laboratory testing is driven by clinical suspicion. If the rash appears benign, then laboratory studies are generally unnecessary.

This said, toxic-appearing patients with an unexplained rash and fever may benefit from a complete blood  count with differential, along with a platelet count, chemistry panel, liver function tests, and blood cultures. The platelet count may implicate thrombocytopenia as a cause of petechiae. In the patient with unstable vital signs or who appears dehydrated, a chemistry panel will detect acidosis as well as renal or electrolyte abnormalities. Patients with Stevens-Johnson syndrome or toxic epidermal necrolysis, in particular, may have electrolyte abnormalities from fluid losses through the disrupted skin. Liver function tests may tell the clinician if there is hepatitis, which is occasionally seen with some drug hypersensitivity reactions.15

Serology is occasionally useful. A Venereal Disease Research Laboratory (VDRL) or fluorescent treponemal antibodies (FTA) test for syphilis can be diagnostic in a person with papulosquamous lesions suggestive of the disease. If Lyme disease is suspected, then an IgM antibody to Lyme or rising IgG titers may be sent for confirmation. However, the sensitivity and specificity are not perfect, and a positive test does not discriminate between previous and current infection. Serologic testing for Lyme disease is recommended only when the physician believes the patient has a 20% or greater chance of harboring active disease.16


In certain cases, aspirates or scrapings of pustular fluid may be obtained for Gram's stain (useful in suspected cases of anthrax or gonococcemia). When evaluating an unknown ulceration, Tzanck smears are 74% sensitive to herpes infections.17 Potassium hydroxide preparations to look for hyphae are sometimes useful in the diagnosis of yeast infections.

Punch Biopsies

Punch biopsies are relatively simple to do. A circular cutting instrument called a trephine is pushed vertically into the skin with rotational movements until the instrument sinks into subcutaneous tissue. The operator then lifts the specimen with a toothless forceps, and the base is cut with iris scissors. Specimens can then be sent in a sterile container for Gram's staining or other tests (e.g., immunofluorescence).18

Emergency physicians familiar with the technique can use punch biopsies to identify a variety of lesions. For example, a febrile patient with a petechial/purpuric rash may have either meningococcemia or Rocky Mountain spotted fever. A Gram's stain of a punch biopsy specimen may identify the organism and streamline antibiotic selection. The sensitivity for punch biopsy in meningococcemia is approximately 72%.19


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Last Modified: 12/12/2017
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