Light urticaria L56.3

Merklen, 1904; Duke coined the term "solar urticaria" in 1923 (cited by S. Goetze).

Rare, highly acute, IgE-mediated, light dermatosis with erythema and wheals appearing within 5-10 minutes after light exposure in the exposed skin areas.

The type and severity of the disease depends on the duration of exposure, the type of sun exposure, the location and extent of the sunlight-exposed skin areas. Also known are delayed reactions of more than 1 hour after irradiation, delayed regression of > 24 h, as well as anaphylactic reactions (in case of whole body exposure) possibly with involvement of the oral mucosa.

Some authors divide the light urticaria into 5 groups according to the UV-spectrometer that triggers them:

• type I (UVB): 280-320nm
• Type II(UVA): 320-400nm
• Type III type V: 400-800 nm

0.08% of urticaria cases. This disease is not observed in populations with a dark-skinned population.

IgE-mediated, allergic reaction of the immediate type to an unknown, photo-induced autoallergen; a "serum factor" plays a role in some patients It is assumed that incident light is absorbed by a chromophore. This chromophore is activated to become a photoallergen against which an IgE antibody is directed. The IgE-antibody is placed on the surface of the mast cell. The accumulation of the photoallergen results in the release of histamine and the formation of wheals.

The action spectrum can cover the entire UV range. However, the action spectrum is preferably in the UVA wave range and visible light (400-600nm). More seldom is a triggering by UVB (280-320 nm) and infrared. Some patients have a history of urticaria.

Mostly occurring in young adults (predominantly 20 to 40 years of age), rarely in old age (7 to 8 decades of age) or in infancy (1 to 6 years of age).

Erythema and wheals appear within a few minutes after light exposure in the exposed areas. Skin symptoms subside within minutes to hours after the end of exposure. Subjectively, the patients suffer from extremely severe itching. In case of extensive infestation possible formation of shock fragments or complete shock state.

Fixed light urticaria: A special form of light urticaria is fixed light urticaria. Here the wheals develop only in certain regions of the body. The rest of the integument remains free of symptoms even after irradiation.

Light urticaria of the delayed type: here, a local urticarial reaction does not occur after minutes as usual but only after hours.

Associated diseases can be:

• Polymorphic light dermatosis
• various forms of urticaria (heat, pressure and cold urticaria)
• Churg-Strauss Syndrome
• Stevens-Johnson syndrome
• Hypereosinophilic dermatitis

The clinical picture with the acute symptoms, the detection of wheals and the clear solar distribution pattern is diagnostic.

Acute urticaria of other genesis.

• Careful light-hardening can be attempted. Exact testing of the triggering spectrum, then determination of the individually suitable light-hardening. Positive effects were achieved with systemic PUVA therapy.
• Attempt of rapid hardening by means of UVA1.
• Alternative to PUVA-therapy: narrow band UVB.

Antihistamines in the usual dosage are often not sufficient. Higher dosages or combinations of different antihistamines are often not sufficient. Antihistamines lead to success in mild cases.

Glucocorticoids + antihistamines: In the initial phase, symptom-related emergency therapy as in acute urticaria: if necessary, high-dose systemic glucocorticoids 100-150 mg prednisolone equivalent i.v. and antihistamines i.v. (e.g. Fenistil). In case of shock symptoms, proceed according to shock, anaphylactic.

Alternative: chloroquine (Remark: clinical effects are not very satisfactory)

Alternative: Plasmapheresis can lead to a noticeable improvement of the findings, especially in patients with serum factor.

Alternative immunosuppressive drugs: In severe cases immunosuppressive drugs (e.g. Ciclosporin A) can be tried.

Alternative IVIG: Improvement of symptoms has been described after IVIG.

Alternative Omalizumab: Experience with Omalizumab, an IgE antibody, has been increasingly positive. An attempt to cure seems to be justified in case of resistance to therapy (see Allergo J Int (2016:16)

Months - to years of disease progression with symptoms that are more annoying than threatening. The regression can occur spontaneously after months or years. In larger studies a complete healing of the symptoms could be proven in 25% of the patients within a 10-year period. Rarely is a severe manifestation of the clinical symptoms with shock conditions.

Prescription of broadband sun protection products with a correspondingly high sun protection factor.

Continuous administration of antihistamines such as desloratadine (e.g. Aerius) 1 tbl/day or levocetirizine (e.g. Xusal) 1 tbl/day.

If necessary, test with chloroquine (e.g. Resochin) initial dose 250 mg/day p.o., later 2 times/week 250 mg p.o.

Detection of photodermatosis:

• Photoprovocation test on skin not exposed to the sun (buttocks, abdomen), since chronic exposure to light increases the urticaria threshold. According to the individual action spectrum, characteristic wheals are often triggered after the light staircase with UVA and UVB has been carried out. In some patients (in larger collectives this is about 15%) visible light (slide projector) can also be provoked.
• > 90% of patients can be provoked by UVA.
• In order to determine the exact action spectrum as well as the minimum quad dose ( MUD = minimum urticarial dose), additional irradiations of 250-700 nm with a monochromator are useful, if possible (but they are not available in clinical routine).
• Alternatively, cautious (controlled) irradiation with natural sunlight can be performed.
• The test reactions are read immediately and up to one hour after irradiation.
• Serum factor test (no longer relevant in practice): collection of patient serum and irradiation of the serum with 0.1 J/cm2 UVB, 10 J/cm2 UVA or with visible light (depending on the action spectrum determined) and subsequent intracutaneous injection of 0.05-0.1 ml serum and a control with 0.05-0.1 ml 0.9% NaCl-Lsg. After 5 and 15 minutes, assess whether a wheal forms at the injection site.

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