Fluorescent fibre-optic confocal imaging of lesional and non-lesional psoriatic skin compared with normal skin in vivo

Background/aims Fibre‐optic confocal imaging (FOCI) allows non‐invasive visualization of live skin in vivo. A contrast agent, a fluorophore, is injected in the dermis. FOCI images are optical sections from a horizontal (en face) view. The aim was to study epidermis and the cellular structure of keratinocytes of psoriatic plaques and adjacent non‐lesional with healthy skin as a reference. Methods Twelve patients with stable plaque psoriasis were studied and compared with a control group of eight healthy individuals. Fluorescein sodium was used as fluorophore. A hand held fibre‐optic laser scanner (Stratum®; Optiscan Pty., Melbourne, Australia) was used. The study included morphometric analyses. Results The confocal in vivo images demonstrated characteristic features of epidermis and keratinocytes in lesional and non‐lesional skin vs. healthy skin. Morphometry based on FOCI demonstrated an approximately 30% increased width of keratinocytes of psoriatic skin vs. healthy control, and the number of keratinocytes per viewing field was reduced. FOCI allowed non‐invasive visualization of cell nuclei and parakeratosis of psoriatic epidermis. The horizontal width of dermal papillae of psoriatic skin was increased by approximately 50% as compared with healthy skin, and the flow of erythrocytes in the papillar vessels could be observed in real‐time. Conclusion FOCI can directly visualize essential epidermal structures of plaque psoriasis in vivo, in real‐time and with cellular resolution without the need of taking biopsies and thus without disturbing the natural state of the skin. FOCI is a versatile future tool for non‐invasive microscopic diagnosis and therapy follow‐up of psoriasis.