Chapter 9

#### High-Yield Facts

• 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.

#### History

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?

#### Physical Examination

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

Morphology describes the general appearance of a rash and can be described in terms of primary and secondary lesions.13 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 ...

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