Approach to the Adult Rash

Published on 10/02/2015 by admin

Filed under Emergency Medicine

Last modified 10/02/2015

Print this page

rate 1 star rate 2 star rate 3 star rate 4 star rate 5 star
Your rating: none, Average: 0 (0 votes)

This article have been viewed 12019 times

191 Approach to the Adult Rash

Pathophysiology

A rash is a skin eruption that has a defined morphology and location. The morphology of the rash is usually distinct and related to the pathophysiologic dysfunction of the skin. Most severe rashes begin as exanthems (from the Greek exanthema, which means “breaking out,” and anthos, which means “flowering”). These rashes subsequently take on a particular morphology, characteristic lesions, or distribution. Table 191.1 delineates the most common terms used for skin lesions. Understanding these terms helps one better document progression of disease and facilitates communication with consulting physicians.

Table 191.1 Common Terms for Skin Lesions

TERM DESCRIPTION
Lesion Single small diseased area
Macule Circumscribed area of change without elevation
Rash Skin eruption that is more extensive than a single lesion
Papule Solid raised lesion < 1 cm
Nodule Solid raised lesion > 1 cm
Plaque Raised confluence of papules > 1 cm
Pustule Fluid-filled area containing purulence
Vesicle Fluid-filled area < 1 cm containing clear fluid
Bullae Fluid-filled area > 1 cm
Petechiae Pinpoint flat round spots < 3 mm caused by intradermal bleeding that do not blanch
Purpura Hemorrhagic area > 3 mm that does not blanch
Exanthem Rash outside the body (skin)
Enanthem Rash inside the body (mucous membranes)

Presenting Signs and Symptoms

Eliciting the initial distribution and progression of a rash is essential. Additionally, the involvement of palms, soles, and mucous membrane is of key importance. It should be kept in mind that dysphasia, as well as eye or genital irritation, may be a manifestation of as mucosal involvement and is often the initial symptom of several life-threatening conditions. The rash’s rapidity of progression is also an essential in diagnosis. Box 191.1 categorizes these important findings.

Specific Signs

Two signs are important in the evaluation of these rashes: the Nikolsky sign and the Asboe-Hansen sign. A positive Nikolsky sign (Fig. 191.1) is noted when slight rubbing of the skin results in exfoliation of the outermost layer with lateral extension of the erosion into the intact skin. The area of denuded skin is pink and tender. The Asboe-Hansen sign (indirect Nikolsky sign or Nikolsky II sign) is extension of a blister into normal skin with the application of light pressure on the top of the blister. All patients with tender, blistering, or sloughing skin should be evaluated serially for these important signs.

Differential Diagnoses and Medical Decision Making

History taking is an essential component in formulating appropriate differential diagnoses and guiding medical decision making. Inquiry regarding the patient’s travel, medical, occupational, recreational, and medicinal history is required. Once the history and physical examination are complete, in-depth evaluation of the rash is in order. The differential diagnoses can be narrowed by categorizing the rash as erythematous, maculopapular, petechial/purpuric, or vesiculobullous.

The Algorithmic Approach

Erythematous Rashes

These rashes are characterized by diffuse redness of the skin as a result of capillary congestion. Erythematous rashes are differentiated by the presence or absence of fever and the Nikolsky sign (Fig. 191.2).1 If a Nikolsky sign is present, the diagnosis is narrowed substantially, usually to TEN in adults and to staphylococcal scalded skin syndrome (SSSS), generally in infants and young children. If fever is present without a Nikolsky sign, the differential diagnosis includes Kawasaki disease, scarlet fever, erythroderma, and toxic shock syndrome (TSS). Patients with an erythematous rash but without a fever or Nikolsky sign may be having an anaphylactic reaction or a reaction to vancomycin, scombroid, or alcohol exposure. Please refer to Chapter 18 for review of SSSS, Kawasaki disease, and scarlet fever. Refer to Chapter 192 for review of TEN, TSS, and erythroderma.

image

Fig. 191.2 Algorithm for erythematous rashes.

SSS, Scalded skin syndrome; TEN, toxic epidermal necrolysis

(From Murphy-Lavoie H, LeGros TL. Emergent diagnosis of the unknown rash: an algorithmic approach. Emerg Med 2010;42[3]:6-17.)

Maculopapular Rashes

The term maculopapule is a portmanteau of macule and papule. Maculopapular rashes are differentiated by the distribution of the rash and systemic toxicity (Fig. 191.3). Patients with centrally distributed rashes who appear toxic and febrile have a wide differential diagnosis; however, it is paramount that patients living in endemic areas be assessed for Lyme disease. Those with centrally distributed rashes but no signs of toxicity usually have either a drug reaction or pityriasis rosea. Patients with peripherally distributed rashes have a broader differential diagnosis that is dependent on systemic toxicity, the presence or absence of target lesions, and whether the rash is located on the flexor or extensor surfaces. Target lesions (Fig. 191.4) are pathognomonic for SJS or erythema multiforme (EM). The target lesion of Lyme disease is usually a single large bull’s eye that measures at least 5 cm in diameter (erythema migrans). Patients with peripheral lesions and systemic toxicity but without target lesions require emergency evaluation for meningococcemia, RMSF, and syphilis. Nontoxic patients with a peripherally distributed rash and no target lesions require further assessment for flexor involvement (scabies or eczema) or extensor involvement (psoriasis). Please refer to Table 191.2 for review of EM minor and major. See Chapter 18 for review of viral exanthems. Please refer to Chapter 192 for review of Lyme disease, meningococcemia, RMSF, SJS, and syphilis.

image

Fig. 191.3 Algorithm for maculopapular rashes.

(From Murphy-Lavoie H, LeGros TL. Emergent diagnosis of the unknown rash: an algorithmic approach. Emerg Med 2010;42[3]:6-17.)

Table 191.2 Erythema Multiforme

Buy Membership for Emergency Medicine Category to continue reading. Learn more here
Causes Possibly autoimmune
Unknown in 50%
Exposures Infections: herpes simplex, Mycoplasma, fungi
Drug exposures: sulfa and other antibiotics, anticonvulsants
Classification Erythema multiforme minor Erythema multiforme major
Description Mild, self-limited rash