DERMATOLOGY FOR THE USMLE BASICS OF DERMATOLOGY (6) COMMON TERM IN DERMATOLOGY (lesions)

DERMATOLOGY FOR THE USMLE

BASICS OF DERMATOLOGY (6)

COMMON TERM IN DERMATOLOGY (lesions)

A	Primary Lesions The basic initial lesion of a skin disease. Primary lesions have not been altered by temporal changes or exogenous factors such as trauma, scratching or infections. Specific descriptive terms are: √ Macule: Discolored area ≤ 1 cm in diameter. Nonpalpable; when a finger is run over the skin, no lesion is felt (eg, tinea versicolor). √ Patch: Discolored area > 1 cm in diameter, nonpalpable (eg, vitiligo). √ Papule: ≤ 1 cm in diameter. Palpable (raised), commonly called “a bump.” Papules can be flat-topped, pedunculated, sessile, umbilicated, acuminate, dome-shaped or verrucous (eg, molluscum contagiosum). √ Plaque: > 1 cm in diameter. Thickened and elevated palpable skin, often formed by confluence of papules (eg, psoriasis). √ Nodule: ≥ 1 cm in diameter. Elevated and circumscribed solid lesion, usually located within the dermis or subcutaneous tissue (eg, lipoma). √ Cyst: Enclosed cavity containing liquid or semisolid substance (eg, epidermoid cyst). √ Vesicle: ≤ 1 cm in diameter. Circumscribed and elevated serum or blood-filled blister (eg, herpes simplex). √ Bulla: > 1 cm in diameter. Fluid or blood-filled blister (eg, bullous pemphigoid).
B	Secondary Lesions Alteration of primary lesion by evolution over time or exogenous factors (eg, trauma, scratching or infection). √ Pustule: Small, circumscribed, pus-filled papule. Usually white or yellow on physical exam (eg, acne vulgaris). √ Abscess: Walled-off purulent material, usually within the dermis. Fluctuant on physical exam (eg, furuncle). √ Scale: Superficial dead epidermal cells appearing as whitish or gray friable material adherent to a lesion (eg, pityriasis rosea). √ Crust: Yellow-to-brown dried exudate atop lesion (“scab”). May occur secondary to superimposed bacterial infection (eg, impetigo). √ Lichenification: Thickening and roughening of the skin with accentuated white skin markings. Usually occurs secondary to chronic rubbing or scratching (eg, lichen simplex chronicus). √ Scar: Fibrous tissue that has replaced damaged skin (eg, burns). √ Keloid: Abnormal scar that continues beyond the boundaries of the original skin injury. May occur after minor trauma (eg, piercing). √ Erosion: Shallow, focal loss of skin surface involving the epidermis only (eg, intertrigo). √ Excoriation: Superficial linear erosion secondary to scratching. Commonly seen in pruritic disorders (eg, atopic dermatitis). √ Fissure: Thin, linear skin cleft; may involve the epidermis and dermis (eg, tinea pedis). √ Ulcer: Deep loss of skin surface that may involve the epidermis, dermis and subcutaneous tissue (eg, stasis ulcer).
C	Miscellaneous Lesions √ Hemorrhagic lesions: Red-to-purpuric lesions caused by blood extravasation into the skin, nonblanchable and nonpalpable. Commonly seen in platelet, coagulation and vascular disorders (eg, disseminated intravascular coagulation). »Petechiae (< 0.5 cm in diameter) »Purpura (0.5 to 1 cm in diameter) »Ecchymosis (> 1 cm in diameter) √ Telangiectasia: Prominent fine and irregular dilated superficial blood vessels; blanchable (eg, hereditary hemorrhagic telangiectasia). √ Spider angioma: Small, red, vascular macule with radiating spiderlike superficial vessels; blanchable. Commonly seen in patients with hyperestrogenism (eg, cirrhosis). √ Wheal (hive): Superficial dermal swelling leading to a transient, edematous papule or plaque (eg, urticaria).