The age of the patient, onset, duration, progression, associatedcutaneous symptoms (pain, pruritus), and associated systemicsigns or symptoms (fever, malaise, weight loss) are importantclues. Obtaining an accurate description of the original lesionimproves diagnostic accuracy. Over-the-counter remediesmay alter the appearance of a rash dramatically. Patients oftendo not consider a topical antibiotic or anti-itch medication astreatment. Thus it is important to probe deeply with relatedquestions in the history. Other important information includesa history of allergies, environmental exposure, travel history,previous treatment, affected contacts, and family history.
A careful examination of the skin requires a visual and a tactile assessment. Examination of the skin over the entire body must be performed systematically. Mucous membranes, hair, nails, and teeth, all of ectodermal origin, also may be involved in cutaneous disorders and should be assessed.
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A descriptive nomenclature of skin lesions helps with generating a differential diagnosis and also with communication between health care providers. Determination of the primary lesion and secondary change is the cornerstone of dermatologic diagnosis. A primary lesion is defined as the basic lesion that arises de novo and is most characteristic of the disease process (Table 188-1 and Fig. 188-1). Primary lesions are rarely seen on a patient at the time of presentation, as most lesions are altered by time or external factors such as
Flat, nonpalpable lesion <1 cm in diameter Patch
Similar to macule, but >1 cm in diameter
Papule Elevated, solid lesion <1 cm in diameter
Plaque Similar to papule, but >1 cm in diameter; has a flat and broad surface in contrast to a nodule
Nodule Similar to papule, but >1 cm in diameter; has a rounded surface in contrast to a plaque
Tumor Similar to nodule, but implies a neoplastic growth rather than an inflammatory process
Bulla Similar to vesicle, but >1 cm in diameter
Pustule Pus-filled epidermal lesion, which may have an initial papular phase and often is surrounded by erythema
Purpura Macule or papule resulting from extravasated blood into the skin; does not blanch with pressure
Petechia Similar to purpura, but less than a few millimeters in diameter
Ecchymosis Larger, hemorrhagic patch or plaque resulting from extravasated blood
Wheal (hive) Pink, edematous papules and plaques that vary greatly in size and configuration; characterized by transient nature with individual lesions resolving within 24 hours
Telangiectasia Collection of small superficial red blood vessels
Milia Superficial, white, small epidermal keratin cysts
Comedo Plug of keratin and sebum within the orifice of a hair follicle, which can be open (whitehead) or closed (blackhead); characteristic lesion of acne vulgaris
Cyst Papule or nodule with an epidermal lining composed of fluid or solid material
Figure 188-1 Morphology of primary skin lesions. A, Flat lesions. B, Palpable lesions. C, Fluid-filled lesions. D, Special primary lesions. (From Swartz MH: Textbook of Physical Diagnosis: History and Examination, Philadelphia, 1989, WB Saunders.) medication applied, secondary infection, or physical manipulation (e.g., scratching). A search for the primary lesion often proves worthwhile and focuses the differential diagnosis to a category of lesion that is specific for the underlying diagnosis. On occasion, two different types of primary lesions may be present. In most cases, secondary lesions are the residue, or result, of the effects of the primary lesion. They may be created by scratching or secondary infection and may be seen in the absence of a primary lesion (Table 188-2).