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The skilful doctor knows by observation, the mediocre doctor by interrogation, the ordinary doctor by palpation.

Chang Chung-ching (c. AD 170–196)

The diagnosis of skin problems depends on astute clinical skills based on a systematic history and examination and, of course, experience. If the diagnosis is in doubt, it is appropriate to refer the patient to a skilled cooperative consultant, as the referral process is an excellent educational opportunity for the GP. Another opinion from a colleague/s in a group practice is also very educative. At least, cross-referencing the skin lesion with a colour atlas facilitates the learning process.

Terminology of skin lesions

Primary lesions

  • Macule. Circumscribed area of altered skin colour (Latin for stain) without elevation <1 cm diameter (see FIG. 121.1).

  • Patch. Macule of >1 cm diameter (see FIG. 121.1).

  • Papule. Palpable mass on skin surface <0.5 cm diameter (see FIG. 121.2).

  • Maculopapule. A raised and discoloured circumscribed lesion.

  • Nodule. Circumscribed palpable mass >0.5 cm diameter (see FIG. 121.2).

  • Plaque. A flat-topped palpable mass >1 cm diameter.

  • Wheal. An area of dermal oedema (can be any size), which is pale and compressible.

  • Angio-oedema. A diffuse area of oedema extending into subcutaneous tissue.

  • Vesicle. A fluid-filled blister <0.5 cm in diameter (see FIG. 121.3).

  • Bulla. A vesicle >0.5 cm diameter (see FIG. 121.3).

  • Pustule. A visible collection of pus in the skin <1 cm diameter.

  • Abscess. A localised collection of pus in a cavity >1 cm diameter.

  • Furuncle. A purulent infected hair follicle; includes:

    • folliculitis (small furuncles)

    • boils (larger furuncles)

  • Carbuncle. A cluster of boils discharging through several openings.

  • Purpura. Bleeding into the skin (dermis) appearing as multiple haemorrhages. May be macular or papular.

  • Petechiae. Purpuric lesions 2 mm or less in diameter.

  • Ecchymosis. Larger purpuric lesion.

  • Haematoma. A swelling from gross bleeding.

  • Telangiectasia. Visible dilatation of small cutaneous blood vessels.

  • Comedo. A plug of keratin and sebum in a dilated pilosebaceous gland.

  • ‘Blackhead’. An open comedo.

  • ‘Whitehead’. A closed comedo.

  • Erythema. Redness of the skin due to increased vascularity.

  • Milium. Tiny white cyst containing keratin, from occlusion of pilosebaceous gland.

  • Papilloma. Warty projection above the skin surface.

Secondary lesions

  • Scales. An accumulation of excess keratin that presents as flaking.

  • Crusts (scabs). Superficial dried secretions (serum and exudate).

  • Ulcer. A circumscribed deep defect with loss of all the epidermis and part or all of the dermis (see FIG. 121.4); they usually heal with scarring.

  • Erosion. A skin defect with complete or ...

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