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June 2008: Sun exposure

By Dr Nigel Stollery

By Dr Nigel Stollery

1 Solar lentigines

Solar lentigines are small (<5mm diameter), sharply demarcated pigmented macules surrounded by normal skin. They are more common in Fitzpatrick skin types I and II and occur on sun-exposed areas such as the face, arms, hands and upper trunk.

They are most commonly seen in patients aged 30-50 years but appear at an earlier age in individuals who regularly use sunbeds. Although they are commonly termed ‘liver spots' they are not associated with liver disease.

A recent study, which compared 145 individuals with solar lentigines with 145 matched controls, showed that multiple solar lentigines on the upper back and shoulders are a clinical marker of past severe sunburn and may be used to identify those at risk of malignant melanoma.1

2 Actinic keratoses

Chronic exposure to UV radiation is a significant factor in the ageing process of skin. In the early stages this results in the development of solar lentigines and wrinkles, followed by actinic keratoses and, in a small percentage, malignancy.

Actinic keratoses commonly occur on the backs of the hands, and on the scalp in men. They develop as areas of rough and hyperkeratotic skin, with associated erythema and crusting.

If left untreated, around 5% will develop into a squamous cell carcinoma. Treatment options include cryotherapy with liquid nitrogen, topical therapies such as diclofenac, imiquimod and 5-fluorouracil, or excision.

Patients should be made aware of the aetiology of their condition and advised to avoid the sun or take adequate sun protection measures such as wearing hats and covering up with protective clothing and/or applying sunscreen (ideally at least SPF 30 with UVA 4*) regularly.

3 Sunburn

Sunburn is now known to be a significant aetiological factor in both skin ageing and the development of malignancies such as squamous cell carcinoma and malignant melanoma.

Sunburn is an acute cutaneous inflammatory reaction to excessive exposure to UVB (290-320nm). This is usually through sun exposure but may also result from using sunbeds, phototherapy and arc lamps.

Risk factors for sunburn include skin type, especially Fitzpatrick type I, geographical location (proximity to the equator1 or high above sea level), length of exposure, time of day2 and exposure to photosensitising agents such as parsnips, celery, bergamot, limes and figs.

Sunburn is more common in men and children.3,4 In mild cases the skin will become red and uncomfortable, whereas in more severe cases there may be blistering and significant first-degree burns, with associated fever, nausea and vomiting.

Treatment with anti-inflammatory drugs such as aspirin and fluid replacement are usually all that is required. A short course of prednisolone (40-60mg/day) may be helpful in severe cases.

4 Polymorphic light eruption

Polymorphic light eruption is the most common acquired photosensitivity syndrome, affecting 10-25% of individuals during their lifetime. It presents a few hours after UV exposure as an itchy, papular eruption on some, but not all, sun-exposed areas and typically lasts for seven days.

The rash usually affects the forearms, V of the neck and upper chest, with relative sparing of the face and dorsum of the hands. In most cases the severity of the eruption decreases with each subsequent exposure, the so-called ‘hardening response', so it is worse in the spring and improves through the year.

Acute attacks can be treated with potent topical or oral steroids (20mg per day for five days). In severe, recurrent cases, desensitisation therapy with narrow band UVB or PUVA can be useful.

5 Bowen's disease

Chronic exposure to UV light is the main aetiological factor in the development of Bowen's disease. Although described as a carcinoma in situ, only 5% of cases progress to an invasive squamous cell carcinoma and metastases are rare. Both sexes are affected equally and incidence increases with age.

Lesions are small, erythematous, scaly and resemble psoriatic plaques. In two-thirds of cases the plaques occur as solitary lesions and grow slowly. Lesions can occur on any sun-exposed site but are more common on the legs.

Diagnosis is usually made by skin biopsy and affected areas are treated with cryotherapy, topical 5-fluorouracil, imiquimod or excision.

6 Solar urticaria

In solar urticaria (sun allergy), weals, or sometimes just erythema, develop on sun-exposed areas within minutes of exposure and may last for hours.

Severe solar urticaria can be a psychologically distressing and debilitating condition. In common with other forms of urticaria, the release of histamine from mast cells triggers the skin changes. In severe cases an anaphylactic reaction may also occur, with associated nausea, bronchospasm, lightheadedness and occasionally syncope.

In milder cases standard sun protection measures and non-sedating antihistamines may be all that is required. In more severe cases desensitisation by phototherapy with increasing levels of UV exposure or plasmaphoresis may be helpful.

The condition will persist indefinitely in the majority of patients.

7 Basal cell carcinoma

Basal cell carcinomas (BCCs) are most common in patients aged 55-75 years and 75-85% occur on the head and neck. The primary aetiological factor is UV exposure, with risk related to the degree of exposure and skin type. The incidence of BCC is increasing annually throughout the world and there are 50,000 new cases of non-melanoma skin cancer per year in the UK, of which 80% are BCCs.5

There are various types of BCC. Rodent ulcers present as small, pearly nodules with a central indentation. The lesions have a rolled raised edge which, when viewed at a right angle, appears to have a white, pearl-like appearance. Telangiectasia may be present and the lesions tend to grow. Other types include superficial BCCs and the scar-like morphoeic BCC.

Unlike melanomas, BCCs are very rarely fatal and anxious patients can be reassured. If left untreated, lesions can ulcerate and become painful.

Treatment options include cryotherapy, curettage and cautery, excisional surgery, Mohs micrographic surgery, radiotherapy, 5-fluorouracil, intralesional interferon, photodynamic therapy and imiquimod.

8 Malignant melanoma

One of the most serious hazards of UV exposure is the risk of developing a malignant melanoma. Malignant melanoma is more common in women than men and tends to occur on the lower legs in the former and back in the latter. The incidence in the UK is rising rapidly, from 2 per 100,000 in 1971 to 10.1 per 100,000 in 2001 (11.7 for women).6

NICE recommends that all suspicious pigmented lesions should be referred to secondary care under the two-week wait rule. With 1,500 deaths in England and Wales in 2002,4 malignant melanoma is a major cause of skin cancer mortality, though only represents 10% of the total number of cases of all skin cancers.

1 Solar lentigines 2 Actinic keratoses 3 Sunburn 4 Polymorphic light eruption 5 Bowen's disease 6 Solar urticaria 7 Basal cell carcinoma 8 Malignant melanoma Author

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

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