Description of Lesions

If a skin lesion is found, it should be classified as a primary or secondary lesion, and its shape and distribution should be described. Primary lesions arise from normal skin. They result from anatomic changes in the epidermis, dermis, or subcutaneous tissue. The primary lesion is the most characteristic lesion of the skin disorder. Secondary lesions result from changes in the primary lesion. They develop during the course of the cutaneous disease.

The first step in identifying a skin disorder is to characterize the appearance of the primary lesion. In the description of the skin lesion, the clinician should note whether the lesion is flat or raised and whether it is solid or contains fluid. A penlight is often useful to determine whether the lesion is slightly elevated. If a penlight is directed to one side of a lesion, a shadow forms according to the height of the lesion.

The location of the lesion on the body is important. Therefore, the distribution of the eruption is crucial in making a diagnosis. It may be rewarding to inspect a patient's clothing when contact dermatitis or pediculosis (infestation with lice) is suspected. On occasion, occupational exposure may leave traces of contamination with oils or other materials that may be visible on the clothing and help in the assessment.

The three specific criteria for a dermatologic diagnosis are based on morphology, configuration, and distribution, morphology being the most important. The purpose of the following section is to acquaint the reader with the morphologic features of the primary and secondary lesions and the vocabulary associated with them.

Primary and Secondary Lesions

To facilitate reading, the primary lesions are listed here with regard to being flat or elevated and solid or fluid-filled (Figs. 8-17 to 8-20). There is no ''standard'' size of a primary lesion. The dimensions indicated are only approximate. The secondary lesions are grouped according

Primary Skin Lesions: Nonpalpable, Flat

Lesion Characteristics

Examples

Macule Smaller than 1 cm

Freckles, moles

Patch Greater than 1 cm

Vitiligo, cafe au lait spots

Figure 8-17

Primary Skin Lesions: Palpable, Solid Mass Lesion Characteristics

Papule Smaller than 1 cm

Nodule

Tumor Plaque

Wheal

Greater than 2 cm

Flat, elevated, superficial papule with surface area greater than height

Superficial area of cutaneous edema

Examples

Nevus, wart

Erythema nodosum

Neoplasms

Psoriasis, seborrheic keratosis

Hives, insect bite

Figure 8-18

Papule

Superficial area of cutaneous edema

Papule

Wheal

Tumor

Nodule

Wheal

Tumor

Nodule

Primary Skin Lesions: Palpable, Fluid Filled

Lesion

Characteristics

Examples

Vesicle

Smaller than 1 cm; filled with serous fluid

Blister, herpes simplex

Bulla

Greater than 1 cm; filled with serous fluid

Blister, pemphigus vulgaris

Pustule

Similar to vesicle; filled with pus

Acne, impetigo

Special Primary Skin Lesions

Lesion Characteristics

Comedo Plugged opening of sebaceous gland

Burrow Smaller than 10 mm, raised tunnel

Cyst Palpable lesion filled with semiliquid material or fluid

Abscess A specific type of primary lesion with localized accumulation of purulent material in the dermis or subcutis; in general, the accumulation is so deep that the pus is not visible from the skin's surface

Furuncle A specific type of primary lesion that is a necrotizing form of inflammation of a hair follicle

Carbuncle A coalescence of several furuncles

Milia Tiny, keratin-filled cysts representing an accumulation of keratin in the distal portion of the sweat gland

Examples

Blackhead Scabies

Sebaceous cyst

Figure 8-20

Comedo

Milia Tiny, keratin-filled cysts representing an accumulation of keratin in the distal portion of the sweat gland

Comedo

Esquema Paisatge Les Coves

Furuncle

Milia Carbuncle

Furuncle to their occurrence below or above the plane of the skin (Figs. 8-21 and 8-22). Other important lesions are shown and described in Figure 8-23.

Configuration of Skin Lesions

It is not essential for the examiner to make a definitive diagnosis of all skin disease. A careful description of the lesion, the pattern of distribution, and the arrangement of the lesion often points to a group of related disease states with similar manifesting dermatologic signs (e.g., confluent macular rashes, bullous diseases, grouped vesicles, papular rashes on an erythematous base). For example, grouped urticarial lesions with a central depression are suggestive of insect bites. Figure 8-24 lists the terms used to describe the configurations of lesions.

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