Identifying Primary and Secondary Skin Lesions
Primary skin lesions are present at the onset of a disease. In contrast, secondary skin lesions result from changes over time caused by disease progression, manipulation (scratching, picking, rubbing), or treatment. These 2 types of skin lesions can be differentiated as follows:
* Bulla-a vesicle (see definition below) greater than 5 mm in diameter
* Cyst-an elevated, circumscribed area of the skin filled with liquid or semisolid fluid
* Macule-a flat, circumscribed area; can be brown, red, white, or tan
* Nodule-an elevated, firm, circumscribed, and palpable area greater than 5 mm in diameter; can involve all skin layers
* Papule-an elevated, palpable, firm, circumscribed area generally less than 5 mm in diameter
* Plaque-an elevated, flat-topped, firm, rough, superficial papule greater than 2 cm in diameter; papules can coalesce to form plaques
* Pustule-an elevated, superficial area that is similar to a vesicle but filled with pus
* Vesicle-an elevated, circumscribed, superficial, fluid-filled blister less than 5 mm in diameter
* Wheal-an elevated, irregularly shaped area of cutaneous edema; wheals are solid, transient, and changeable, with a variable diameter; can be red, pale pink, or white.
* Crust-a slightly elevated area of variable size; consists of dried serum, blood, or purulent exudate
* Excoriation-linear scratches that may or may not be denuded
* Lichenification-rough, thickened epidermis; accentuated skin markings caused by rubbing or scratching (eg, chronic eczema and lichen simplex)
* Scale-heaped-up keratinized cells; flakey exfoliation; irregular; thick or thin; dry or oily; variable size; can be white or tan.