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Sun damage

By Dr Nigel Stollery

By Dr Nigel Stollery

Malignant melanoma

There are various types of melanoma, but the most common is the superficial spreading variety. These lesions will eventually invade deeper tissues but before this stage they undergo a radial growth phase. With no curative treatment apart from excision, early diagnosis and referral is of paramount importance. In accordance with current national guidance, any suspicious pigmented lesions need to be referred urgently using the two-week wait system to a dermatology service. In the case, pictured here, the melanoma has not been treated during its initial stages and nodular areas can be clearly seen at the points where invasion is starting. (This melanoma measures approximately 5 cm across.)

Lentigenes

Lentigenes are light or dark brown macules that occur on sun-exposed areas especially the backs of the hands and forearms. They are usually discrete lesions and may have an irregular outline and pigmentation. Simple lentigenes often arise in childhood as a few scattered lesions. Solar or senile lentigenes are more common in later life and are often referred to as liver spots when they occur on the backs of the hands. In contrast to ephelides (freckles), lentigenes have increased numbers of melanocytes and need to be distinguished from the more serious lentigo maligna. This usually requires a small incisional biopsy. Treatment is not necessary, but laser therapy may be used for cosmetic improvement. Adequate sun protection should always be applied.

Actinic keratosis

Actinic keratoses occur as discrete rough surfaced lesions on sun-exposed areas. These unsightly lesions are frequently seen on bald men, and their numbers increase with age. They occasionally cause soreness but are usually asymptomatic. A small percentage will progress to squamous cell carcinoma so treatment is usually advised. In mild cases, a topical diclofenac sodium preparation licensed for this condition can be applied. In more severe cases

5-fluorouracil can be used. The latter needs to be applied to the whole area of sun-exposed skin in the vicinity of the lesions, not just the lesions themselves, as sub-clinical lesions will then be treated. Patients need to be warned that the treatment can induce a marked inflammatory reaction leaving the area red and sore.

Sunburn

Sunburn is an acute inflammatory response to exposure to excess UVB. This usually occurs as an erythema which develops 4-6 hours after the exposure but may not peak until 16-24 hours. This delay is thought to represent the time it takes for the damaged epidermal cells to mount an inflammatory response. In the absence of further exposure a typical reaction will usually settle over 2-3 days, but in more severe cases exfoliation and hyperpigmentation may occur.

In almost all cases sunburn is a self-limiting condition. However, occasionally if the sunburn is very extensive, with blistering, hospitalisation may be required for pain relief, dressings and fluid replacement.

Solar urticaria

In solar urticaria exposure to ultraviolet radiation or visible sunlight leads to an urticarial rash. The ultraviolet radiation causes the release of histamine from mast cells as it does in other forms of urticaria. Patients usually present with reports of weals on most, or more usually, all sun-exposed areas within a few minutes of exposure after which the rash settles within 1-2 hours.

The area is usually very pruritic and this is often associated with a burning sensation. In severe cases this may also be associated with a reaction similar to anaphylaxis which may include, bronchospasm, hypotension and rarely syncope. Treatment consists of sun avoidance, using sunscreens, wearing appropriate clothing and taking oral antihistamines. In severe, recurrent cases graduated exposure to UVA or PUVA may help.

Polymorphic light eruption

Polymorphic light eruption (PLE) is the most common of the acquired photosensitivity syndromes affecting 10-15% of people at some time during their lives. In the milder cases, this condition is sometimes referred to as prickly heat or sun allergy, though prickly heat in the true sense actually refers to miliaria rubra. PLE tends to arise each spring after the initial exposure to UV light. In the majority of cases, sun avoidance is the key to management. Covering up with suitable clothing and regular use of sunscreens are essential. In acute attacks, especially those associated with foreign holidays, a course of oral steroids (20mg daily) taken for 5 days after the onset of the rash may be needed. In severe cases, desensitisation therapy with narrow band UVB or PUVA should be considered, although this has to be repeated every springtime.

Polymorphic light eruption Malignant melanoma Solar urticaria Sunburn Lentigenes Actinic keratosis Author

Dr Nigel Stollery,
GP, Kibworth Leicestershire and clinical assistant in dermatology, Leicester Royal Infirmary

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