Morphology of primary and secondary skin lesions

Chapter 2 Morphology of primary and secondary skin lesions



Donna M. Corvette, MD




1. Why do dermatologists use words that no one else understands?
The language of dermatology is unique. It encompasses terms that rarely, if ever, are used in other medical specialties. The use of these correct dermatologic terms is important to accurately describe skin lesions to dermatologists during telephone calls and during rounds and teaching. A good description of a skin lesion enables the listener to formulate a series of differential diagnoses, whereas a poor one does not.

2. But why are the descriptions so long?
Use of appropriate terminology and important clues, such as configuration and skin distribution, effectively paints an accurate picture for the listener. Use of vague terms—spot, bump, rash, and lesion—is not helpful. Such vocabulary is counterproductive to formulating an accurate differential diagnoses. “Grouped vesicles on an erythematous base” immediately suggests herpes simplex, and “brown, friable ‘stuck-on’ papules” accurately describes seborrheic keratoses. “Well-demarcated, erythematous plaques with micaceous, silvery scales located on extensor surfaces” is suggestive of psoriasis. “Violaceous, polygonal papules with Wickham’s striae located on flexural surfaces” is consistent with lichen planus. On the other hand, “red, scaly rash on the foot” describes an enormous, nebulous group of disorders.

3. How can I possibly learn the language of dermatology?
First, learn the definitions of the various primary, secondary, and special skin lesions. Each of these groups consists of a short list of terms that specifies basic types. Then, follow this simple template when describing skin lesions:
• Size

• Color or additional descriptive terms (e.g., pigmentation, shape)

• Type of primary, secondary, or special skin lesion (e.g., papule, macule)

• Arrangement (e.g., grouped lesions)

• Distribution (e.g., truncal, generalized)

This template provides a systematic way to add adjectives to the type of lesion. Repetition is key; practice using the template when describing skin lesions.


4. What is a primary skin lesion?
It is the initial lesion that has not been altered by trauma, manipulation (scratching, scrubbing), or natural regression over time. Examples include:

• Macules

• Wheals

• Papules

• Vesicles

• Plaques

• Bullae

• Patches

• Pustules

• Nodules

• Cysts

5. How is each of the primary lesions defined?
See Table 2-1.

6. How do you determine whether a lesion is flat or raised?
Palpation is the most reliable method, but side-lighting also helps. It can be difficult to distinguish a macule from a papule or a patch from a plaque in a photograph.

7. How does a primary lesion differ from a secondary lesion?
Secondary skin lesions are created by scratching, scrubbing, or infection. They may also develop normally with time. For example, the primary lesion in a sunburn is a macular erythema (although it could also be a blister), but with resolution, scale and increased pigmentation become prominent. Examples of secondary lesions include:
• Crusts

• Scale

• Ulcers

• Fissures

• Excoriations

• Scars

• Erosions

• Postinflammatory hyperpigmentation

8. How are secondary skin lesions defined?
See Table 2-2.

9. What is a maculopapular eruption?
A dermatitic lesion that is composed of both macules and papules. Maculopapular eruptions are commonly seen with viral exanthems and drug-induced reactions. The cutaneous eruption of measles is an example of a maculopapular eruption.

10. Give some examples of special skin lesions.
• Telangiectasias

• Purpura

• Petechiae

• Comedones

• Burrows

• Target lesions

11. What are telangiectasias?
Telangiectasias (Fig. 2-1) are small, dilated, superficial blood vessels (capillaries, arterioles, or venules) that blanch (disappear) with pressure.

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Apr 26, 2016 | Posted by in Dermatology | Comments Off on Morphology of primary and secondary skin lesions

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