Chapter 9: Approach to the Patient with Rash

• Primary lesions are uncomplicated abnormalities which represent the initial pathologic change. Secondary changes reflect progression of disease.

• Diagnosis depends upon identification of the primary lesion. Other features, such as distribution, configuration, and color assist in narrowing the diagnosis. These features along with a focused history and knowledge of key clinical features usually result in a specific diagnosis of dermatologic 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.

Emergency physicians are faced with a vast range of dermatologic problems. At any given time, there may be a straightforward case of urticaria or a more serious presentation of toxic epidermal necrolysis (TEN) waiting to be seen. The role of the emergency physician is not to diagnose every dermatologic “zebra” but rather to distinguish the trivial from the serious and to identify those conditions which require urgent care.

The history can be broken down to a series of questions including:

1. What specifically prompted the patient to seek medical care? What do they think is causing the rash?

2. Where did the lesions originate?

3. When did the lesions first develop and what has been the progression of the rash?

4. Was there any prodrome to the lesions? What are the associated symptoms?

5. How does it feel? Does it itch, hurt, or sting?

6. What made it better or worse? What treatment was applied?

7. How is the patient's general health including allergies? What medications do they take regularly or intermittently?

8. What kind of exposures have they had, including occupation (applicable for adolescent population), travel, foods, and contacts?

9. Family history of any skin-related disorders?

Dermatology is a visual specialty and diagnosis relies heavily on careful inspection of the skin. The examination should be performed in a well-lit area. The patient should be appropriately exposed so that the entire eruption can be evaluated for distribution and configuration. After evaluation of the eruption at a distance, individual lesions are examined. Palpation of the rash confirms consistency and depth. For purposes of this systematic approach, the most important objective of the physical examination is to characterize the morphology of the primary lesion. A thorough description of a rash should include morphology, color, configuration, and distribution.

Morphology describes the general appearance of a rash and can be described in terms of primary and secondary lesions.^1–3 Primary lesions are uncomplicated abnormalities which represent the initial pathologic change. Secondary changes reflect progression of disease such as excoriation, infection, or keratinization. The morphologic expression of a dermatologic condition is the basis on which all diagnoses are founded. In some cases, the appearance is distinctive enough to make a diagnosis at a glance (i.e., the grouped vesicular lesions of herpes simplex). In other cases, the appearance may be modified by scratching, secondary infection, or prior treatment. Most importantly, it is important to recognize that skin disease may evolve over time.

Primary Lesions

Macule: Circumscribed, flat discoloration of <1 cm in diameter; examples include ash-leaf spots, flat nevi, and freckles. Macules may constitute the whole or part of a rash or may represent the early phase.

Patch: Flat discoloration that is >1 cm in diameter and circumscribed; examples include vitiligo or tinea versicolor. Patches often have a very fine scale on the surface.

Papule: Circumscribed, superficial, solid elevated lesion <1 cm in diameter; examples include warts, elevated nevi, insect bites, and molluscum contagiosum.

Plaque: A lesion >1 cm in diameter elevated, flat top, superficial lesion; examples include psoriasis and pityriasis rosea.

Vesicle: Fluid-filled lesion <1 cm in diameter; examples include herpes simplex and varicella.

Bulla: Fluid-filled lesion >1 cm in diameter; examples include staphylococcal scalded skin syndrome and bullous impetigo.

Pustule: Pus-filled lesion; examples include acne and folliculitis.

Nodule: Lesion <1 cm in diameter with depth, may be subsurface, suprasurface, or at level of surface.

Tumor: Solid lesion >1 cm with depth, which may be subsurface, suprasurface, or at level of surface.

Petechiae: Pinpoint <1 cm flat, round red spots under the skin surface, because of deposits of blood and/or pigment; examples include drug eruption, Rocky Mountain spotted fever.

Purpura: Visible collection of blood/pigment >1 cm in diameter; examples include Henoch–Schonlein purpura and idiopathic thrombocytopenia purpura.

Wheal: Transient, edematous papule, or plaque with pale center and pink margin, peripheral erythema; examples include hives and insect bites.

Secondary Lesions

Scale: Dry or greasy masses of keratin ranging from fine and delicate to coarse. Generally implies a pathologic process in the epidermis.

Crust: Dried exudate (serum, pus, or blood).

Excoriation: Punctate or linear abrasions generally caused by scratching.

Fissure: Linear crack or cleavage on skin, with sharply defined margins.

Ulcer: Depressed lesion because of epidermal or dermal tissue loss.

Scar: Permanent lesion resulting from the process of repair/replacement of connective tissue.

Lichenification: Area of increased epidermal thickness with accentuation of skin.

Rashes may present with few or numerous lesions. The primary morphologic lesion may be discrete or confluent. Distinctive diagnostic features such as distribution, configuration, and color may trigger immediate recognition. In addition, findings such as the texture (i.e., the sandpaper texture of scarlet fever) or other abnormalities such as a positive Nikolsky'ssign (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 (i.e., acne—face; dermatophyte infection—groin, foot, scalp; scabies—web spaces, wrists). Widespread lesions may demonstrate symmetry (Gianotti–Crosti syndrome or erythema multiforme) or may be asymmetrically distributed to different areas of the body (viral exanthema). Figure 9-1 illustrates common distributive patterns.

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 or form a specific shape (i.e., arciform shape of tinea corporis). Certain dermatologic conditions manifest in a classic configuration (i.e., grouped vesicles of herpes simplex). Figure 9-2 illustrates common configurations.

An Algorithmic Approach

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. Once the primary lesion has been identified, diagnostic details should be sought: secondary changes, distribution, and configuration. Historic features usually 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 vs. drug eruption). Figures 9-3 to 9-7 illustrate an algorithmic approach to rashes based upon the primary lesion.

True Emergencies in the Pediatric Dermatologic Presentation

Several dermatologic conditions have significant morbidity and potential mortality making prompt diagnosis and initiation of therapy essential for optimal outcome.

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's sign. Several drugs are known to cause these conditions including 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

is 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's 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 scarlatiniform skin lesions. Gastrointestinal 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 diagnosing Kawasaki disease were recently revised and now include: fever >5 days without another probable etiology as well as at least four 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 and edema of hands or 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 child with meningococcal disease can be difficult to differentiate from more benign disease processes. Meningeal infection often manifests as headache, fever, stiff neck, nausea, vomiting, photophobia, and altered mental status. 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

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 disseminated intravascular coagulation.⁹

The approach to the pediatric dermatology patient in the ED may appear daunting; however, with a systematic approach, one can more readily and successfully arrive at a diagnosis and manage the patient effectively.