Dermatology

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What is livedo reticularis?

A net-like subcutaneous rash, most commonly seen on the lower limbs - may be seen in conditions such as: SLE, rheumatoid arthritis, polyarteritis nodosa, antiphospholipid syndrome, homocystinuria, dermatomyositis, cholesterol emboli syndrome.

What is Gardner's syndrome?

A hereditary dominant condition, comprising multiple osteomas, cutaneous and soft tissue tumours and
polyposis coli.

What are the factors which predispose to an increased prevalence of venous leg ulceration in females?

Venous ulcers are caused by incompetent valves in the veins of the lower leg, especially in the perforators. These incompetent valves cause blood to be squeezed out into the superficial veins, when the calf muscles are contracted, instead of upwards towards the heart. Dilation of superficial veins occurs (varicosities) and the subsequent raised venous pressure results in oedema, venous eczema and ulceration. Valves may become damaged following the venous hypertension that occurs in pregnant women, and resulatant varicose veins increase the risk of venous ulcers. Age and immobility are also big risk factors, and women have a longer lifespan than men, so there are more elderly, immobile women.

What are the indications for patch testing?

Patch testing is appropriate for patients with atopic eczema or dermatitis to find out if there is a response to a specific antigen. It is rarely appropriate for food allergies that cause urticaria or anaphalaxis. It tests for a type IV hypersensitivity reaction, not type I.

What type of hypersensitivity is atopic eczema (atopic dermatitis)?

Atopy is an immediate type I hypersensitivity reaction, which is IgE mediated.

What type of hypersensitivity is contact dermatitis?

A type IV hypersensitivity reaction. It can be caused by an irritant, an allergen or sunlight. It is T cell mediated.

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