Outline of Dermatologic Diagnosis Part II

HISTORY Demographics Age, race, sex, occupation. History; 1. Constitutional symptoms • “Acute illness” syndrome: headaches, chills, feverishness, weakness • “Chronic illness” syndrome: fatigue, weakness, anorexia, weight loss, malaise 2. History of skin lesions. Seven key questions: • When? Onset • Where? Site of onset • Does it itch or hurt? Symptoms • How has it spread (pattern of spread)? Evolution • How have individual lesions changed? Evolution • Provocative factors? Heat, cold, sun, exercise, travel history, drug ingestion, pregnancy, season • Previous treatment(s)? Topical and systemic, 3. General history of present illness as indicated by clinical situation, with particular attention to constitutional and prodromal symptoms 4. Past medical history • Operations • Illnesses (hospitalized?) • Allergies, especially drug allergies • Medications (present and past) • Habits (smoking, alcohol intake, drug abuse) • Atopic history (asthma, hay fever, eczema) 5. Family medical history: (particularly of psoriasis, atopy, melanoma, xanthomas, tuberous sclerosis) 6. Social history: with particular reference to occupation, hobbies, exposures, travel , injecting drug use. 7. Sexual history: history of risk factors of HIV: blood transfusions, IV drugs, sexually active, multiple partners, sexually transmitted disease? SPECIAL CLINICAL AND LABORATORY AIDS TO DERMATOLOGIC DIAGNOSIS: 1. A magnifying lens(hand lens 7×) : To examine lesions for fine morphologic detail, magnification is especially helpful in the diagnosis of -lupus erythematosus (follicular plugging), -lichen planus (Wickham striae), -basal cell carcinomas (translucence and telangiectasia) 2. Wood lamp (ultraviolet long-wave light , “black” light): is valuable in the diagnosis of certain skin and hair diseases. With the Wood lamp (365 nm) . Fluorescence is seen in some fungal infections, erythrasma and Pseudomonas infections. Some subtle disorders of pigmentation can be seen more clearly under Wood’s light e.g. the pale patches of tuberous sclerosis, low-grade vitiligo and pityriasis versicolor, and the darker café au lait patches of neurofibromatosis). 3.Diascopy consists: of firmly pressing a microscopic slide or a glass spatula over a skin lesion. The examiner will find this procedure of special value in determining whether the red color of a macule or papule is due to: 1.capillary dilatation(erythema) 2.or to extravasation of blood(purpura) that does not blanch. 4.Photography : mostly digital nowadays, helps to record the baseline appearance of a lesion or rash, so that change can be assessed objectively at later visits. 5.Dermoscopy A hand lens with built-in lighting and a magnification of 10× to 30× is called a dermatoscope and permits the noninvasive inspection of deeper layers of the epidermis and beyond. This is particularly useful in the distinction of benign and malignant growth patterns in pigmented lesions. The lesion is covered with ultrasound gel, mineral oil, alcohol or water and then, illuminated and observed at 10⋅ magnification with a hand-held dermatoscope . The gel or fluid eliminates surface reflection and makes the horny layer translucent so that pigmented structures in the epidermis and superficial dermis, and the superficial vascular plexus can be assessed. CLINICAL TESTS 1.Patch testing: is used to document and validate a diagnosis of allergic contact sensitization and identify the causative agent. Substances to be tested are applied to the skin in shallow cups (Finn chambers), a fixed with a tape and left in place for 24–48 h. Contact hypersensitivity will show as a papular vesicular reaction that develops within 48–72 h when the test is read. Patch testing. Individual allergens are tested on strips obtained from companies that sell individual allergens in syringes. Many positive reactions of varying intensity appeared. 2.Photopatch testing is a combination of patch testing and UV irradiation of the test site and is used to document photoallergy. 3.Prick testing: is used to determine type I allergies. A drop of a solution containing a minute concentration of the allergen is placed on the skin and the skin is pierced through this drop with a needle. Piercing should not go beyond the papillary body. A positive reaction will appear as a wheal within 20 min. The patient has to be under observation for possible anaphylaxis. 4.Acetowhitening: facilitates detection of subclinical penile or vulvar warts. Gauze saturated with 5% acetic acid (white vinegar) is wrapped around the glans penis or used on the cervix and anus. After 5–10 min, the penis or vulva is inspected with a 10⋅ hand lens. Warts appear as small white papules. LABORATORY TESTS 1.Potassium hydroxide preparations for fungal infections: If a fungal infection is suspected, scales or plucked hairs can be dissolved in an aqueous solution of 20% potassium hydroxide (KOH) containing 40% dimethyl sulphoxide (DMSO). The scale from the edge of a scaling lesion is vigorously scraped on to a glass slide with a No. 15 scalpel blade. Other samples can include nail clippings, the roofs of blisters, hair pluckings and the contents of pustules when a candidal infection is suspected. A drop or two of the KOH solution is run under the cover slip . After 5–10 min the mount is examined under a microscope with the condenser lens lowered to increase contrast. Nail clippings take longer to clear – up to a couple of hours. With experience, fungal and candidal hyphae can be readily detected . No heat is required if DMSO is included in the KOH solution. Preparing a skin scraping for microscopy by adding potassium hydroxide (KOH) from a pipette. Fungal hyphae in a potassium hydroxide (KOH) preparation. The polygonal shadows in the background are horny layer cells. 2.Cytology (Tzanck smear): Cytology can aid the diagnosis of viral infections such as herpes simplex and zoster, and of bullous diseases such as pemphigus. A blister roof is removed and the cells from the base of the blister are scraped off with a No. 10 or 15 surgical blade. 3.Skin biopsy: Biopsy of skin lesions is useful to establish or confirm a clinical diagnosis. A piece of tissue is removed surgically for histological examination and sometimes for other tests (e.g. culture for organisms). Skin biopsies may be incisional, when just part of a lesion is removed, or excisional, when the whole lesion is cut out. -Scalpel biopsy -Punch biopsy 4.Microscopic Examination of Scales, Crusts, Serum, and Hair -Gram stains of smears and cultures of exudates and of tissue minces should be made in lesions suspected of being bacterial or yeast ( Candida albicans ) infections.