Health Significance Of The Clinical Examinations And Laboratory Investigations Of Skin Disorders
The skin is the largest organ in the body and constitutes 15% of the body weight. The skin closely reflects disorders occurring in the internal organ systems and several cutaneous disorders have systemic components. Skin disorders are widespread in developing countries (especially in the tropics, like India). Clinical examination of a dermatological lesion is not complete without a full systemic examination and investigations. Dermatological examination should be performed under conditions of proper lighting.
Points to be stressed in the history: Particular emphasis should be laid on evolutions of the lesion, associated symptoms like itching, pain, fever, etc and the effect of all forms of previous treatment.
Primary Skin Manifestations
Macules: They are flat lesions which are neither raised nor depressed from the surrounding normal skin but showing colour changes. They do not show textural alteration.
Papules: These are circumscribed solid elevations situated superficially on the skin, varying in size from 1mm to 1cm in size, eg, verrucase or warts, lichen planus, popular rash.
Nodules: These are circumscribed solid lesions larger than 1cm in diameter situated deeper than papules in the skin or subcutaneous tissue, eg, erythema nodosum, lupus vulgaris, tertiary syphilis.
Tumours: These are lesions, usually larger and more deeply situated than nodules, e..g., neurofibromata, epitheliomata.
Wheals: These are soft pinkish or whitish evanescent swellings of varying sizes seen specifically in urticaria, e.g. insect bite, angioedema.
Vesicles and bullae: Vesicles are circumscribed collections of free fluid within the layers of the skin. Eg, chickenpox, herpes simplex, herpes zoster. Bullae are collections of fluid larger than vesicles, e.g pemphigus vulgaris, erythema multiforme, burns.
Pustules: These are thin walled superficial collections of pus, eg, small pox, pustular psoriasis.
Crusts (Scabs): These are formed of dried up serum, blood or pus or a combination of these.
Ulcer: This results from loss or destruction of superficial tissue which may involve the epidermis and part of the dermis (e.g ecthyma) or deep subcutaneous tissue (e.g necrotic ulcers, stasis ulcers).
Lichenification: The normal wrinkles of the skin become prominent and they enclose flat-topped, hyperpigmented papules which may also show mild scalling, eg, lichen simplex chronicus, neurodermatitis, Lichenfication results from constant irritation such as rubbing or scratching.
Pigmentary Changes:Hyperpigmentation may be seen following acute or chronic inflammatory skin diseases. Sometimes, dark-skinned races may react with hypopigmentation instead of hyperpigmentation.
Excoriation: This is loss of epidermis brought about by scratching.
Atrophy: Atrophy of the skin manifests as bypopigmented, wrinkled areas. The connective tissue in the dermis is involved mostly. The dermal appendages and subcutaneous tissues are also lost.
Slcerosis: The dermis and subcutaneous tissue are indurated. The uverlying epidermis is thinned out, eg, scleroderma.
A full dermatological diagnosis may necessitate several investigations.
General investigations: In many diseases, like diabetes, jaundice and acanthosis nigricans, full systemic investigations are necessary for diagnosing the systemic illness.
- Scarping of scales and examination for fungal infection: The scales are suspended in 20% potassium hydroxide which dissolves keratin, but no fungal filaments and spores, and examined under the miscroscope.
- Culture of material for bacteria and fungi in appropriate media.
- Dark- field examination of serum from ulcers on genitalia and skin or mucous surfaces for spirochetes.
- Skin slit scrapings are done to demonstrate M. Leprae. Smears are made from the dermis through a small slit in the skin, using a scalpel and the material is stained for AFB. This method can be used for diagnosing onchocerciasis and cutaneous leishmaniasis.
- Microscopic examination of scraped material from skin lesions may reveal parasites like sarcoptes scabei.
Skin tests for detecting allergy
Patch test: These tests are used in detecting the allergen involved in a suspected case of contact allergic dermatitis.
Photo-patch test: This is used to detect allergens which cause contact photosensitivity.
Intradermal tests: The antigen is introduced intradermally in low concentration. These are particularly useful for testing drug and food allergy. Other tests such as “prick test” and “scratch test” are used in detecting the allergen in food or drug allergy. The suspected substance is applied as a solution on the surface of the skin and it is allowed entry through small pricks or scratches.
© 2014 Funom Theophilus Makama