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Latest update 28/09/10
This chapter is set out as follows:
Classification
Photodermatoses can be split into 2 groups:
- Photosensitive dermatoses– only happen as a result of light. Most are immunologically mediated except those related to chemicals (drugs, porphyria) and DNA repair (xeroderma pigmentosum)
- Photoaggravated dermatoses – these are pre-existing skin conditions that can be made worse with light e.g. lupus erythematosus, dermaotomyositis, herpes simplex, Darier’s disease, pellagra and some cases of rosacea
This chapter will focus on photosensitive dermatoses
Aetiology of photosensitive dermatoses
- Idiopathic
- Polymorphic light eruption (PLE)
- Actinic prurigo
- Chronic actinic dermatitis
- Solar urticaria
- Hydroa vacciniforme
- Genetic
- Metabolic
- Exogenous
- Drug-induced photosensitivity
- Photocontact allergic reactions
- Phytophotodermatitis
Ultraviolet radiation
- UVA as opposed to UVB is largely responsible for the photodermatoses
- UVB is the predominant factor in sunburn
- Sunscreens are much more effective against UVB than UVA
- Most glass protects only from UVB, whereas laminated windows (e.g. in some front car window screens) also protect against UVA
- For more information on UV protection please click here
History & examination
- Age and sex – genondermatoses such as xeroderma pigmentosum are usually apparent in childhood, polymorphic light eruption (PLE) usually has an onset in later childhood and is more commonly seen in woman, chronic actinic dermatitis is mainly a disorder of older men
- Timing of the eruption in relation to sun exposure / use of sunscreen – solar urticaria occurs within minutes, PLE many hours. Patients with chronic actinic dermatitis or porphyria cutanea tarda may not be aware that their symptoms are worse in the sun. Symptoms made worse after application of sunscreen suggest a photocontact allergic dermatitis to the sunscreen
- Timing of the eruption in relation to season – PLE is typically prominent in the spring and improves later in the summer
- Pain – most photosensitive rashes cause itch. A burning pain is typical for erythropoieitc protoporphyria
- Window glass – most glass only blocks UVB, those front car that are laminated protect from both UVA & UVB
- Medications – ask about all prescribed and OTC drugs, systemic and topical. Always enquire about quinine
- Family history – important for the porphyrias
- Distribution – photosensitive dermatoses mainly (but not exclusively) affect the UV exposed areas of the skin. The classical presentation of several of the photosensitive rashes (e.g. drug-induced, chronic actinic dermatitis) is that there will be relative sparing of shaded areas of the face (lower eyelids, beneath the nose, behind the ears and under the chin) in comparison with airborne contact dermatitis. However patients with more severe / chronic forms of photosensitive dermatoses will not have sparing of these sites. Involvement of the dorsal aspects of the hands is more patchy
- Scale - if the rash heals with scaling it is more likely to reprsent an eczematous eruption (e.g. drug-induced or chronic actinic dermatitis) as opposed to PLE or solar urticaria
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Figure 1 - Photosensitive distribuion
The red areas show those parts of the face most affected by photo-sensitive dermatoses
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Figure 2 - Drug-induced photosensitivity
Note the relative sparing of photo-protected areas
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Figure 3 - Airborne contact dermatitis to sesquiterpene lactones in plants
Sesquiterpene lactones are allergens found in the compositae species of plants such as dandelions and chrysanthemums. They are not photosenitising agents but instead cause an allergic contact dermatitis. The rash does not spare photoprotected areas
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Investigations
- If lupus needs to be excluded check FBC, PV, routine biochemistry, ANA and ENA Ro and La antibodies
- Porphyria – see later under porphyria
- Phototesting – can help diagnose photosensitive rashes where there is diagnostic uncertainty. It can also be of use in assessing some patients with moderate-severe photosensitive dermatoses so as to aid management
- Photopatch testing – is of use for patients suspected of having a photo-contact allergic dermatitis to sunscreen. The only other relevant topical preparations that could give to such a reaction are the NSAIDs
Photosensitive dermatoses
- Polymorphic light eruption and juvenile spring eruption
- Drug-induced photodermatoses
- Chronic actinic dermatitis
- Solar urticaria
- Porphyria
- Actinic prurigo
- Hydroa vacciniforme
- Sunbeds and skin fragility syndrome
Polymorphic light eruption
- Incidence - common. Woman > men (15% of women in UK). Can affect any age but more common in teenagers and young adults
- Aetiology - unknown. Triggered by UVA (or UVB)
- History
- Most commonly develops 24 hours after UVR exposure but can occur anyway between 2 hours - 5 days after
- Sunbeds usually triggers rash
- Moderate itch
- Symtpoms ususually settle within a week
- Examination
- Distribution – exposed areas of skin, although less exposed sites can also be affected
- Morphology - ill-defined papules, occasionally vesicular. Background skin usually normal
- In severe cases symptoms may be much more easily provoked and cause a burning sensation. Affected areas can be red and oedematous. Such patients may even be affected by light coming through a car window
- Management
- Provide a patient information leaflet
- In florid cases rule out lupus erythematosus
- UV protection – avoidance, clothing, sunscreens with 5 star UVA protection
- Careful and graduated light exposure in spring may help patients become tolerant before they go on holiday
- Topical - calamine a nd some moisturisers may help keep the skin cool, topical steroids are of little value
- Sedating anti-histamines may help at night
- For moderate cases consider prednisolone EC tablets, 25mg OD for 5 days starting the day before holiday (if away for 2 weeks give an extra 5 days supply, to use if needed)
- For more severe cases refer for consideration of phototesting and further management e.g. phototherapy in spring time to promote tolerance (12-16 exposures gives 4 months of protection), IM depot steroids and in severe cases immunosuppressive drugs
Juvenile spring eruption
- A variant of PLE
- Age - most commonly between 5-14
- Boys > girls
- Symptoms - tiny blisters arise on the rim of the ears causing itch / discomfort, lasting for 2 weeks. Typically arises in early spring
- Management - sun protection, topical corticosteroids
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Figure 4 - PLE |
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Figure 5 - Close up of PLE |
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Figure 6 - PLE |
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Figure 7 - Juvenile spring eruption |
Drug-induced photodermatoses
- Timing from commencing the drug – very variable, from acute to years (quinine can take several years)
- Distribution: predominantly sun-exposed parts of body
- Clinical features include
- Acute sunburn-like reaction
- Redness/scaling – eczematous
- Blistering from contact with psoralen ‘phytophotodermatitis’ – can occur a few days after contact with the offending plant
- Lichenoid
- Low grade ‘pseudoporphyria’ with blistering / skin fragitlity, often backs of hands – especially naproxen and furosemide
- Photo-onycholysis (tetracyclines / ofloxacin / PUVA)
- Pigmentation
- Mechanism can be photo-toxic or photo-allergic
- Drugs with which photosensitivity always or frequently occurs are known as phototoxic reactions. The most commonly associated drugs are psoralens (PUVA therapy, plants) / amiodarone / ciprofloxacin and other quinolones / doxycycline / nalidixic acid
- Photoallergic reactions are rare but important. Most commonly associated drugs are quinine / thiazides / carbamazepine / naproxen and other NSAIDs
- The other group to be aware of are those allergic to sunscreens or topical NSAID, which can cause a photo-contact allergic dermatitis. Where suspected refer for photo-patch testing. It is important to remember that sunscreen can be found in a number of face creams and hair products
Chronic actinic dermatitis
- Aetiology unknown. Mainly found in older men but can arise in younger atopic patient (the prognosis in this latter group is better)
- History – itch and erythema often provoked easily by ultraviolet radiation (UVR). Sensitive to UVB, UVA (most window glass will not protect), and sometimes visible light e.g. from fluorescent lights
- Examination – eczematous. Can go on to develop a chronic dermatitis with thick plaques on sun-exposed areas
- Management:
- UV protection
- Refer for photo-testing and possibly photo-patch testing as some of these patients will also have a number of contact allergies
- In extreme cases immunosuppressants may be needed
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Figure 18 - Chronic actinic dermatitis |
Solar urticaria
- Can affect any age
- History – a sore itchy rash that arises on sun-exposed areas within minutes of exposure and resolves within 30 minutes of sun avoidance
- Triggered by UVA, UVB and visible light
- Differential diagnosis - erythrohepatic protoporphria (see below)
- Management – UV protection, antihistamines (often high dose). Patient often best referred to a dermatologist for consideration of PUVA and immunosuppressive therapy in severe cases. It is also useful to photo-test these patients to assess which wavelengths trigger their symptoms and how easily the urticaria is provoked
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Figure 19 - Solar urticaria |
Porphyria
The porphyrias result from altered metabolism in the haem biosynthesis pathway, leading to an accumulation of porphyrins. There are three main types:
- Porphyria cutanea tarda (PCT)
- The most common type
- Symptoms result from a reaction between the porphyrins in the skin and UVR, which goes on to cause cell damage. Although it is often worse in summer months the patient may not be able to clearly associate symptoms with sun exposure
- Clinical features – skin fragility and blisters on the backs of hands and bald areas of the scalp. Lesions heal slowly and often leave scars. Milia and areas of hyperpigmentation may develop
- Investigations – early morning urine and plasma for porphyrins. Samples should be kept dark (e.g. wrapped in tin foil). Not sending plasma porphyrins may miss a rare and atypical from of variegate porphyria
- PCT is essentially a disease of the liver that presents in the skin. It can be caused by alcohol and higher doses of oestrogens found in some oral contraceptive pills. Patients found to have PCT need to have blood tests for LFTs, autoantibodies, hepatitis B and C screen and a ferritin level for haemachromatosis. Patient with normal bloods should have an annual LFT performed
- Management: identify triggers such as excess alcohol intake. UV protection measures. Refer for specialist management - chloroquine at low dose (half a tablet twice a week) is often the first line of therapy, failing that venesection may be used
- Pseudoporhyria
- In patients with PCT-like symptoms but normal porphrin levels consider a drug cause
- See chapter on adverse cutaneous drug reactions for more information
- Variegate porphyria
- A rare autosomal dominant disorder, with the highest incidence in South Africans of European extraction
- Patients present with skin signs as in PCT but also any of confusion, abdominal pain, peripheral neuropathy or other neurological features
- Blood, urine and faeces need to be examined for porphyrins
- Patient need to be referred and family members screened
- Erythrohepatic protoporphria
- An autosomal dominant disease
- Presents in childhood with severe burning, redness and swelling of exposed areas
- Symptoms arise usually within a few minutes of sun exposure
- Investigation - a blood sample (kept in the dark) for porphyrins
- Management: UV protection. Refer patients for specialist management - treatment is most frequently with oral beta-carotene
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Figure 20 - PCT |
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Figure 21 - PCT |
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Figure 22 - Protoporphyria |
Hydroa vacciniforme
- Rare, usually arises in childhood, more common in boys
- History – recurrent symptoms in summer months, symptoms provoked within hours of sun exposure
- Clinical findings – discrete papules and vesicles arising symmetrically, predominantly on the face, hands or forearms. Other than in mild cases lesions undergo necrosis and heal with pock-like scars
- Patients need to referred for further management including investigations to rule out other photosensitive dermatoses
- The condition is difficult to manage but often resolves in adolescence
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Figure 23 - Hydroa vacciniforme |
Actinic prurigo
- Rare, more common in children especially girls
- History – often starts in first decade of life, lesions itchy. Symptoms most apparent in summer, but not always clearly related to sun exposure and often fail to clear completely in the winter
- Clinical examination – erythematous and often excoriated papules and nodules on exposed areas of skin (non-exposed sites can be affected), the morphology becomes more eczematous with time
- Management – milder cases can be managed by appropriate UV protection measures, emollients and topical steroids. More troublesome cases need to be referred for further investigation and treatment although the condition can be refractory to treatment
- While actinic prurigo usually resolves in the late teens, in others the condition can become chronic
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Figure 24 - Actinic prurigo |
Sunbeds and skin fragility syndrome
- Sunbeds are principally UVA emitting
- They do not afford good protection to the skin because as they do not cause the skin to thicken
- Adverse effects of sunbeds
- Everybody using sunbeds will get increased aging of the skin with the development of wrinkles and lentigo
- Increased risk of skin cancer
- Easy blistering from minor trauma – this is now recognized as the skin fragility syndrome
- Can trigger PLE and other photosensitive / photoaggravated dermatoses
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