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Author: Anoma Ranaweera, Medical Writer, Auckland, New Zealand. 2012.
The term phototherapy or light therapy applies to exposure of the skin to specific wavelengths of light or electromagnetic radiation. There are three ranges of radiation that are applied in phototherapy: infrared (800-3000 nm), visible light (400-800 nm), and ultraviolet radiation (100-400 nm). Treatment of skin disorders most often involves ultraviolet radiation (UVR).
UVA1 is the name given to the waveband of electromagnetic radiation ranging from 340-400nm. UVA1 phototherapy filters out lower wavelengths. It is effective in clearing or controlling a variety of skin diseases.
UVA1 is thought to be effective in treating skin disease by suppressing components of cell-mediated immune function.
UVA1 penetrates deep into the reticular layer of the dermis, acting on fibroblasts, dendritic cells and inflammatory cells, particularly T-cell lymphocytes, as well as mast cells and granulocytes.
UVA1 radiation induces apoptosis (cell death) in the presence of active oxygen molecules, such as singlet oxygen, hydrogen peroxide, or superoxide radicals. It activates programmed (induced) and non-programmed (natural) cell death.
The success of UVA1 in atopic dermatitis was found to result from UVA radiation-induced apoptosis in skin-infiltrating T-helper cells, leading to the loss of T cells from eczematous skin. The effect of UVA1 in inducing T lymphocyte apoptosis may also help treat cutaneous T cell lymphoma (CTCL).
UVA1 also activates fibroblasts to produce matrix metalloproteinases, which break down excess collagen in the extracellular matrix. is why it is useful in sclerosing (scar-like) skin conditions.
UVA1 radiation can be used to treat the following skin diseases:
High-dose UVA1 has also been observed to help:
UVA1 treatment units typically consist of metal halide lamps equipped with special optical filters. Smaller cabinets provide localised therapy, whereas whole-body treatment can be carried out using lie-down or standing UVA1 cabinets.
In North America UVA1 availability is limited, perhaps due to the relatively high equipment costs; UVA1 units are usually two to three times more expensive than conventional whole body narrowband UV treatment units. There are to date no UVA1 units in New Zealand (November 2012). Conventional UVA produced by UV machines in NZ contains about 80% of UVA1. The main difficulty with older machines is the time taken to reach adequate doses of UVA1 so that only a low-dose regimen is practicable.
There are three dosing regimens for UVA1.
The long-term risks of high dose UVA1 are uncertain, so no more than 10-15 treatments per cycle and two cycles per year are recommended.
UVA1 treatment is performed five times a week, usually for 3-4 weeks. However, there are no strict guidelines for its use, and therefore the dose and number of irradiations can be adjusted to each patient individually, taking into account their different skin phototypes and skin problem.
|Indication||Strength of evidence||Recommended dosing regimen||Number of exposures|
|Atopic dermatitis||Randomised controlled trials||Medium-dose||15|
|Sclerosing skin diseases||Randomised controlled trials||Medium- and/or high-dose||20-40|
|T-cell lymphoma||Open studies||Medium- and/or high-dose||10-35|
|Urticaria pigmentosa||Open studies||Medium- and/or high-dose||10-15|
Continued improvement may occur for up to several months after a treatment course. Maintenance phototherapy is not routinely recommended. As the long-term side-effects of UVA1 are unknown, patients younger than 18 years of age, should be treated cautiously.
Adverse effects with UVA1 phototherapy have been classified as acute (short-term) or chronic (long-term).
Acute side effects of UVA1 phototherapy are:
Chronic side-effects of UVA1 phototherapy include:
UVA1 should not be used for patients that have photosensitivity disorders, particularly:
Relative contraindications include:
UVA1 is a form of phototherapy that appears useful for treating atopic dermatitis and sclerotic skin diseases (scleroderma). Overall, the side-effects are well tolerated. The long-term adverse effects and effectiveness in other skin diseases remain uncertain.
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