Rashes may present with few or numerous lesions. The primary morphologic lesion may be discrete or coalesce (Fig. 16–1). Distribution, configuration, and color are common diagnostic features. Additionally, findings such as the texture (i.e., the sandpaper texture of scarlet fever, Fig. 16–2) or other abnormalities such as a positive Nikolsky's sign (epithelial shearing caused by lateral pressure to unblistered skin) may assist in narrowing the diagnosis of a rash.
Many skin diseases have a preferential area of involvement. Eruptions may be widespread or may be localized to specific areas, for example, acne face; dermatophyte infection groin, foot, scalp; wrist scabies. Widespread lesions may demonstrate symmetry (Gianotti–Crosti syndrome or erythema multiforme, Fig. 16–3) or may be asymmetric distributed to different areas of the body (viral exanthema). Figure 16–4 illustrates common distributive patterns.
Symmetric distribution seen with erythema multiforme.
Configuration is the general shape or pattern in which the lesions are arranged. Occasionally, the configuration is diagnostic of the disease. Lesions may be grouped into a pattern (i.e., grouped papules in molluscum contagiosum, Fig. 16–5) or form a specific shape (annular plaque of tinea corporis). Certain dermatologic conditions manifest in a typical configuration, for example, herpes simplex typically present with group vesicles. Figure 16–6 illustrates common configurations.
Grouped papules seen with molluscum contagiosum.
Not uncommonly, the patient with a rash presents a diagnostic challenge to the emergency physician. Similar to the diagnosis of other conditions, a systematic approach to the disease may assist in narrowing the differential diagnosis. The approach described depends heavily on recognition of the primary lesion. Clinicians must be thorough in their attempt to identify the primary lesion. Once the primary lesion has been identified, diagnostic details should be sought; secondary changes, distribution, configuration. Lastly, historic features may help to further refine the diagnosis. Because of overlap of certain clinical conditions, the clinician must recognize (and communicate to the patient) that there are times when it is difficult to narrow the final diagnosis to a single entity. A common example is the febrile patient presenting with a generalized, confluent, erythematous papular rash who was placed on an antibiotic 2 days prior to the eruption (viral exanthem versus drug eruption). Figures 16–7, 16–8, 16–9, 16–10, and 16–11 illustrate an algorithmic approach to rashes based upon the primary lesion.
Algorithmic approach to a rash with macule/patch primary lesion.
Algorithmic approach to a rash with papule/plaque primary lesion.
Algorithmic approach to a rash with vesicle/bulla primary lesion.
Algorithmic approach to a rash with petechiae/purpura.
Algorithmic approach to a rash with pustule primary lesion.
True Emergencies in the Pediatric Dermatologic Presentation
There are certain presentations which are imperative for the emergency physician to diagnose and initiate treatment. The following diseases are those that may result in significant morbidity and/or mortality if missed in the ED setting. We seek to provide only a brief summary of the red flag components of each disease that should alert the ED physician to institute management quickly.
Toxic epidermal necrolysis (TEN) and Stevens–Johnson syndrome (SJS). The typical presentation for each includes constitutional symptoms followed by skin lesions approximately 1 to 3 days later which are characterized by their mucosal membrane involvement. Patients are toxic appearing and this disease spectrum is notoriously rapid in its progression. The skin lesions generally begin as macules that eventually develop into blisters which may have a positive Nikolsky sign. History may be suggestive of recent or current pharmacologic exposures. Typical agents which have been known to cause TEN or SJS include the sulfa-containing drugs, aminopenicillins, quinolones, and cephalosporins. The rash tends to develop 1 to 3 weeks following initiation of drug.4
Staphylococcal scalded skin syndrome, an exfoliative dermatitis which often begins with constitutional symptoms followed by skin lesions that progress from generalized erythema to blisters that rupture leaving a painful red base. One key feature is perioral exudate. A Nikolsky sign is typically present.5
Toxic shock syndrome results from an exotoxin often linked to Staphylococcus aureus and presents with fever, headache, altered mental status, and scarletiniform skin lesions. GI symptoms including diarrhea and vomiting as well as hypotension are also often present.6
Kawasaki disease is a vasculitis which typically manifests in patients younger than 5 years, but may be seen in a child of any age. The disease process usually begins with a fever. The criteria for defining Kawasaki was recently revised and now includes: fever >5 days without another probable etiology as well as at least 4 of the following additional criteria:
- –mucous membrane changes which may be injected pharynx, fissured lips, or the classic strawberry tongue.
- –generalized erythema which evolves into a polymorphous rash.
- –cervical lymphadenopathy.
- –bilateral conjunctival injection.
- –edema (hands, feet).
There is no specific diagnostic test for Kawasaki; therefore, the clinical acumen of the practitioner is crucial in making this diagnosis.7
Meningococcemia. In the early stages, the pediatric patient with meningococcal disease can be difficult to differentiate from more benign disease processes. Meningeal infection often manifests as headache, fever, stiff neck, nausea, vomit, photophobia, and altered mental status. Infants are unable to communicate any of these clinical findings and clinical presentation may include flat fontanelles. The characterizing component of meningococcemia is sudden onset of fever and rash which is typically petechiae and purpura. Hypotension, adrenal failure, and multiorgan failure may be seen as well.8
Anaphylaxis, a life-threatening allergic reaction that manifests in the pediatric patient with urticaria, angioedema, wheezing, dyspnea, hypotension, as well as a myriad of other less common symptoms. Symptoms may develop within seconds to minutes of exposure.9
Purpura fulminans is a life-threatening disease that occurs abruptly. It is a hemorrhagic disease that is often seen in the setting of sepsis. The skin lesions ultimately result in perivascular hemorrhage and necrotic gangrene. The presentation typically includes fever, hypotension, and DIC.10