Category Archives: Dermatology

Diseases of the hair and nails

Both hair and nails are composed of keratin and are derived principally from the epidermal layer. Each may be affected by the same type of disease process, e.g. lichen planus, or altered by conditions that affect primarily the epidermis. DISORDERS OF HAIR GROWTH The extent and distribution of body hair is largely determined genetically. At the time of puberty, terminal hair growth occurs in males on the beard

Diseases of collagen and elastic tissue

The skin contains collagen types I, III and V within the dermis, type IV in the basement membrane, type VII in the anchoring fibrils and type VIII in the endothelium . Abnormalities of these can give rise to various skin disorders. Ehlers-Danlos syndrome This is a heterogeneous group of diseases in which at least nine different varieties have been described. Hyperextensibiliry, fragility and bruising of the

Sunlight and the skin

Controversy exists about the adverse effects of UV radiation exposure on the skin. However, damage can occur in four ways: 1 UVB (medium wavelength 280-310 nm) reaching the earth’s surface is increased by depletion of the stratospheric ozone layer. Synthetic chlorofluorocarbons e.g. some aerosols and refrigerators reaching this zone further compromise this important barrier function. A 1% decrease in t

Disorders of pigmentation

There are many factors that alter the hue of a normal skin. The principal pigments are melanin and haemoglobin or its breakdown products. Carotene, if taken in large amounts in the diet, is concentrated in subcutaneous fat and in keratin, giving a yellow coloration to the skin. The skin can also change its colour by deposition of abnormal substances or by alteration of melanogenesis. These substances include

Vascular and Lymphatic Disorders

Venous ulcers These are confined to the lower limbs and many are postthrombotic. The increased hydrostatic pressure in the veins resulting from incompetent valves is reflected by increased capillary blood pressure. Leakage of plasma under pressure gives rise to perivascular fibrin deposition which may lead to a decrease in oxygen supply, but direct skin oxygen measurements do not support this view. There is a fal

Drug eruptions

Cutaneous eruptions account for one-third of all sideeffects of drugs. It is sometimes difficult to differentiate an eruption due to a drug from one produced by the underlying illness. On occasions the effects of both are relevant to the onset of the rash, for example patients prescribed ampicillin for infectious mononucleosis will often develop a widespread morbilliform rash. Patients often take many drugs

Porphyria Cutanea Tarda

Only the changes seen in porphyria cutanea tarda are considered here. Similar changes in the skin may be seen with variegate porphyria and hereditary coproporphyria. Cutaneous lesions occur on exposure to sunlight. These consist of increased fragility of the skin over the dorsum of the hands, fingers and face and are associated with erythema, blistering and scarring. Hypertrichosis on the sides of the face and be

Squamous carcinoma

This invasive tumour with the ability to metastasize arises from the epidermis (keratinocytes) or skin appendages. It is most commonly seen on previously damaged (e.g. by ultraviolet radiation) or chronically irritated skin. It has also been associated with certain occupations (e.g. chemical carcinogens inducing cancer of the scrotum) or with certain social customs (e.g. tumours on the legs from radiant heat


About one-quarter of patients with systemic sarcoidosis have skin lesions. There are many variants: ERYTHEMA NODOSUM (see p. 1005), a non-specific reaction. NODULES, PAPULES AND PLAQUES, red/blue or brown are seen particularly on the face, nose, ears and neck in chronic sarcoid. This is the most common specific form seen in Caucasians. Ragged cuticle and nail-fold capillary dilatationassociated with dermatomyositi

Naevi and tumours

The skin is a prime target for aberrant growth and tumour formation. It may be in direct contact with ionizing radiation and many chemical substances or microorganisms that may act as inducers of abnormal cellular activity. There are also a large number of different cell types represented within the skin. Many skin tumours are rare and in practice are confined to a few types. Melanocytic naevus (naevocytic