In 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.
Performed 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.
Designed 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 patient’s serum.
Performed 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.
Tissue 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 examined microscopically.
The 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, and examined.
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 ultraviolet light.
Photographs are taken to document the nature and extent of the skin condition and are used to determine progress or improve-ment resulting from treatment.
Copyright © 2018-2020 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.