Autofluorescence-Guided Removal of Psoriatic Tissue

It is known that psoriatic lesions clear and remain cleared if you remove them from the skin. This can be done through surgery and ablative laser therapy. In order for the treatment to be succesful, you need to remove the complete epidermis and a bit of the dermis (the upper part of the skin). In psoriasis, the thickness of that part of the skin can vary significantly. Incomplete removal results in the return of the lesion. A challenge is that you can't easily tell how deep into the skin you are. Not only is the skin quite thin (from 0.1 mm to 1.0 mm), at the boundary they look quite similar. If you go too deep, you get scarring. Thus there is a need to delineate the psoriatic tissue from the healthy tissue.

We think that one way to do that is by looking at the fluorescence of the skin. If you shine a particular shade of blue light on the skin, it gives off red light. But this is only true for the part where the psoriasis can reside. Under normal circumstances this fluorescence is too weak to really see with the eye. Thus we first increase the fluorescence by administering a compound that is used to make the fluorescent molecules in our tissue, 5-aminolevulinic acid (5-ALA). It can be quite difficult to get 5-ALA into the skin. To help the 5-ALA, we use a very superficial lasertreatment to poke minute holes in the skin. The 5-ALA enters the skin and the fluorescence builds up. After a couple of hours, the skin is treated with a laser that can gently remove the tissue. Layer for layer is removed until there is no more fluorescence. At that point we do one more pass to be sure, and then stop. We hope that two months later, the psoriasis is gone and will remain so for at least a year.

We think that the fluorescence helps, but we can't be sure. So for that reason we will also treat a lesion without fluorescence and use the standard method to judge how deep we have treated the skin. And to rule out the possibility that e.g. sun exposure cleared the lesions, we also leave one lesion untreated.

Participants have to travel to the clinic for the treatment and then every three to five days for two weeks. Since we remove the skin, there will be a wound that needs healing and attending to. This will result in some limitations during the wound healing phase. Afterwards, you might see some temporary shifts in pigmentation.