Macule: A circumscribed area of discolored skin, no elevations or vesicles.
Papule (<0.5cm) or nodule (>0.5 cm): A circumscribed area of a skin elevation.
Plaque: A disc-shaped, elevated lesion greater than 2 cm in diameter.
Vesicle: A fluid-filled lesion, less than 0.5 cm in diameter.
Bulla: A fluid-filled lesion, more than 0.5 cm in diameter.
Wheal: A rapidly-formed skin elevation caused by edema of the dermis. Pathognomonic of urticaria.
Comedone: A plug in the sebaceous gland orifice. Seen in acne vulgaris.
Burrow: A grayish, irregular, linear elevation of the horny layer of the skin. Pathognomonic of scabies.
Ulcer: Loss of skin layers including the dermis, healing with a scar.
Abrasion or excoriation: Superficial loss of skin layers, not involving the dermis; no scar involved.
Scar: Connective tissue that replaces lost tissue anywhere in the body.
Tinea Capitis (refer to Fig. 2.1)
Introduction: Ringworm of the scalp.
Organisms: Dermatophyte, Microsporum...