Dermatology is a specialty in which visual inspection allows for rapid diagnosis. A brief physical examination prior to a lengthy history is valuable because some of the classic skin diseases with obvious morphologies allow a “doorway diagnosis” to be established. The tools the physician needs are readily available: magnifying glass, glass slide (for diascopy to determine if a lesion is blanchable), adequate lighting, a flashlight, alcohol pad to remove scale or makeup, scalpel, and at times a Wood lamp. Universal precautions should always be used.
The ability to describe lesions accurately is an important skill, as is the ability to recognize specific patterns. These abilities aid clinicians in their approach to the patient with a cutaneous eruption both in developing a differential diagnosis and while communicating with other physicians. The classic dermatologic lesions are defined in Table 17–1.
TABLE 17–1Dermatologic Diagnostic Descriptions of Lesions of the Skin |Favorite Table|Download (.pdf) TABLE 17–1 Dermatologic Diagnostic Descriptions of Lesions of the Skin
|Primary Cutaneous Lesions ||Secondary Cutaneous Lesions |
Comedone: open and closed dilated pores (blackheads and whiteheads, respectively)
Macule: a circumscribed flat variation of color that is brown, blue, yellow, red, or hyper- or hypopigmented, <1 cm
Patch: a circumscribed flat variation of color that is brown, blue, yellow, red, or hyper- or hypopigmented, >1 cm
Papule: a circumscribed elevation of <1 cm in diameter
Plaque: a circumscribed elevation of >1 cm in diameter
Nodule: a circumscribed elevation often >2 cm in diameter, involves the dermis and at times subcutis
Pustule: a circumscribed collection of purulent fluid that varies in size
Tumor: an elevation of >0.5 cm in diameter
Vesicle: a circumscribed collection of clear fluid <1 cm in diameter
Bulla: a circumscribed collection of clear fluid >1 cm in diameter
Wheal: a firm edematous plaque resulting from infiltration of the dermis with fluid
Erosion: a loss of the epidermis up to the full thickness of the epidermis but not through the basement membrane
Ulcer: a loss of full-thickness epidermis and papillary dermis, reticular dermis, or subcutis
Lichenification: thickening of the epidermis and accentuation of natural skin lines
Atrophy: thinning of the epidermis
Scale: flaking caused by accumulation of stratum corneum (hyperkeratosis) or delayed desquamation
Scar: a thickened, often discolored surface
The skin shields the internal organs from harmful xenobiotics in the environment and maintains internal organ integrity. The adult skin covers an average surface area of 2 m2. Despite its outwardly simple structure and function, the skin is extraordinarily complex. The skin is affected by xenobiotic exposures that occur through many routes. Dermal exposures themselves are important as they account for approximately 7% of all human exposures reported to the American Association of Poison Control Centers (Chap. 130). The clinician must obtain essential information as to the dose, timing, route, and location of exposure. Knowledge of the physical and chemical properties of the xenobiotic can be used to make relevant ...