addition to obtaining the patient’s history, the examiner in-spects the primary
and secondary lesions and their configuration and distribution. Certain
diagnostic procedures may also be used to help identify skin conditions.
to obtain tissue for microscopic examination, a skin biopsy may be obtained by
scalpel excision or by a skin punch in-strument that removes a small core of
tissue. Biopsies are performed on skin nodules, plaques, blisters, and other
lesions to rule out malignancy and to establish an exact diagnosis.
to identify the site of an immune reaction, immuno-fluorescence testing
combines an antigen or antibody with a flu-orochrome dye. Antibodies can be
made fluorescent by attaching them to a dye. Direct immunofluorescence tests on
skin are tech-niques to detect autoantibodies directed against portions of the
skin. The indirect immunofluorescence test detects specific anti-bodies in the
to identify substances to which the patient has devel-oped an allergy, patch
testing involves applying the suspected al-lergens to normal skin under
occlusive patches. The development of redness, fine bumps, or itching is
considered a weak positive reaction; fine blisters, papules, and severe itching
indicate a mod-erately positive reaction; and blisters, pain, and ulceration
indi-cate a strong positive reaction.
samples are scraped from suspected fungal lesions with a scalpel blade
moistened with oil so that the scraped skin adheres to the blade. The scraped
material is transferred to a glass slide, covered with a coverslip, and
Tzanck smear is a test used to examine cells from blistering skin conditions,
such as herpes zoster, varicella, herpes simplex, and all forms of pemphigus.
The secretions from a suspected lesion are applied to a glass slide, stained,
Wood’s light is
a special lamp that produces long-wave ultra-violet rays, which result in a
characteristic dark purple fluores-cence. The color of the fluorescent light is
best seen in a darkened room, where it is possible to differentiate epidermal
from dermal lesions and hypopigmented and hyperpigmented lesions from normal
skin. The patient is reassured that the light is not harm-ful to skin or eyes.
Lesions that still contain melanin almost dis-appear under ultraviolet light,
whereas lesions that are devoid of melanin increase in whiteness with
are taken to document the nature and extent of the skin condition and are used
to determine progress or improve-ment resulting from treatment.