They may be local to the SKIN, or a manifestation of systemic disorders – inherited or acquired. Some major types are described below.
Others appear under their appropriate alphabetical headings: ACNE; ALBINISM; ALOPECIA; ALOPECIA AREATA; APHTHOUS ULCER; BASAL CELL CARCINOMA; BOILS; BOWEN'S DISEASE; CALLOSITIES; CANDIDA; CHEILOSIS; CHEIROPOMPHOLYX; DANDRUFF; DERMATOFIBROMA; DERMATOMYOSITIS; DERMATOPHYTES; DERMOGRAPHISM; ECTHYMA; ERYSIPELAS; ERYTHEMA; ERYTHRASMA; ERYTHRODERMA; ESCHAR; EXANTHEM; FUNGAL AND YEAST INFECTIONS; HAND, FOOT AND MOUTH DISEASE; HERPES GENITALIS; HERPES SIMPLEX; HERPES ZOSTER; IMPETIGO; INTERTRIGO; KELOID; KERATOSIS; LARVA MIGRANS; LICHEN; LUPUS; MADURA FOOT; MELANOMA; MILIARIA; MOLLUSCUM CONTAGIOSUM; MOLE; MYCOSIS FUNGOIDES; NAEVUS; ORF; PEDICULOSIS; PEMPHIGUS; PHOTOCHEMOTHERAPY; PHOTODERMATOSES; PITYRIASIS; PORPHYRIAS; PRURITUS; PSORIASIS; RINGWORM; ROSACEA; SARCOIDOSIS; SCABIES; SCLERODERMA; URTICARIA; VITILIGO; WARTS; XANTHOMATA.
Primary cancer is common and chronic exposure to ultraviolet light is the most important cause. BASAL CELL CARCINOMA is the most common form; squamous cell carcinoma is less common and presents as a growing, usually painless nodule which may ulcerate. Squamous cancer may metastasise by spreading to regional lymph glands and beyond, unlike basal cell cancer. Occupational exposure to chemical carcinogens may cause squamous carcinoma – for example, cancer from pitch warts or the scrotal carcinoma of chimney sweeps exposed to coal dust in earlier centuries. Squamous carcinoma of the lip is associated with clay-pipe smoking.
Cancer may arise from the population of melanocytes of the skin (see MELANOCYTE; MELANOMA).
Apart from these three most frequent forms of skin cancer, various forms of cancer can arise from cells of the dermis, of which LYMPHOMA is the most important (MYCOSIS FUNGOIDES).
Secondary deposits from internal cancer, particularly from the breast, may metastasise to the skin.
These are broadly synonymous, and the terms are frequently interchangeable. Eczema is a pattern of inflammation with many potential causes. Dermatitis is commonly used to suggest an eczema caused by external factors; it is a common pattern of inflammation of the skin characterised by redness and swelling, vesiculation (see VESICLE), and scaling with intense itching and often exudation (weeping). Fissuring, thickening (lichenification – see LICHEN) and secondary bacterial infection may follow. Dermatitis can affect any part of the body. It may be genetically determined or due to other ‘internal’ factors, such as venous HYPERTENSION in a leg, or stress. Often it is ‘external’ in origin – due to strong irritants or chemical allergens. (See also ALLERGY; ALLERGEN.)
is genetic in origin and usually begins in infancy. It may persist for years, and ASTHMA, allergic RHINITIS and ‘hay fever’ – may be associated. Atopic children tend to have multiple allergies, especially to inhaled allergens such as house-dust mite, cat and dog dander and pollens. Allergy to foods is less common but potentially more dangerous, especially if to nuts, when it can cause acute URTICARIA or even ANAPHYLAXIS. Atopic subjects are particularly prone to persistent and multiple verrucae (see WARTS) and mollusca (see MOLLUSCUM CONTAGIOSUM) and to severe HERPES SIMPLEX infections. (See also ATOPY.)
Generalised shedding of skin scales, commonly with ERYTHEMA. Drugs may cause it, or the disorder may be linked with other skin diseases such as benign dermatoses and lupus erythematosus (see under LUPUS).
is an acute vesicular eczema of the palms and soles recurring every summer. Inhaled allergens are a frequent cause.
begins on a lower calf, often in association with PURPURA, swelling and sometimes ulceration. Chronic venous hypertension in the leg, consequent on valvular incompetence in the deep leg veins owing to previous deep vein thrombosis (see VEINS, DISEASES OF), is the usual cause.
A pattern of well-defined plaques of lichenified eczema particularly seen on the neck, ulnar forearms or sides of the calves in subjects under emotional stress (see LICHEN).
Most often seen in an industrial setting (occupational dermatitis), it is due to damage by strong chemicals such as cutting oils, cement, detergents and solvents. In almost all cases the hands are most severely affected.
in contrast, can affect any part of the body depending on the cause – for example, the face (cosmetics), hands (plants, occupational allergens) or soles (rubber boots). Particularly common allergens include metals (nickel and chromate), rubber additives, and adhesives (epoxy resins).
Avoidance of irritants and contact allergens, liberal use of EMOLLIENTS, and topical application of corticosteroid creams and ointments (see CORTICOSTEROIDS) are central.