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Independents' Day

Polymorphous light eruption

Use our quick quiz to check your clinical knowledge

1How common is polymorphous light eruption (PMLE)?

US 10 per cent,

UK 20 per cent.

2Women are more commonly affected than men. True or false?

True. The ratio is 3:1, though this may simply be a reflection of the fact that women are more likely to seek medical help.

3At what age is it more likely to occur?

Onset is generally in the first three decades of life, but may be later in men.

4Describe the rash associated with PMLE?

Papules (greatest incidence), plaques, papulovesicles, and erythema multiforme-like lesions are the most common types. The rash may be a combination of different morphologies.

5What other symptoms may be associated with the rash?

Some patients describe pain and stinging, others may report more generalised flu-like symptoms.

6PMLE is a result of exposure to which type of ultraviolet light?

It may occur with both UVA and UVB. As UVA can penetrate glass the rash may occur without going outside and also despite the use of UVB blocking creams.

7How can PMLE be confirmed?

Photo tests with UVA and UVB light can aid diagnosis, and determine the minimum dose that causes erythema.

8How can PMLE be treated?

Preventive measures remain the mainstay of treatment: sun cream, covering up, avoiding UV light. In some cases prophylactic PUVA treatment in the spring may help. Oral or topical steroids and antihistamines can be useful to control the rash once it has developed.

9In severe cases what other drugs are sometimes used in secondary care?

Nicotinamide, azathioprine, thalidomide, and antimalarials such as hydroxychloroquine.

10Through a season the rash associated with PMLE typically gets worse with each ultraviolet exposure. True or false?

False. With repeated exposure the rash becomes less severe.

This is the basis of prophylactic phototherapy in the spring as a treatment for this condition.

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