Biodistribution of protoporphyrin IX in female genital erosive lichen planus after topical application of hexaminolevulinate

Genital erosive lichen planus (GELP) is a chronic inflammatory disease, in women characterized by painful vulvar and vaginal erosions. To prepare for a clinical trial on photodynamic treatment (PDT), we applied hexyl 5-aminolevulinate hydrochloride (HAL) in clinically normal and affected mucosa in 12 women with GELP using two different doses (6.25 or 50 mg/ml). Biopsies were taken after 30 min and 3 h. The biodistribution of HAL, measured as photoactive protoporphyrin IX (PpIX), was studied using non-invasive superficial fluorescence measurements and microscopic fluorescence photometry. More PpIX was detected after application of 12.5 mg HAL than after 100 mg, with large inter-individual variations. PpIX levels after 3 h were overall higher than after 30 min. PpIX fluorescence was not detected in skin distant to the genital area. In conclusion, 6.25 mg/ml HAL applied for 3 h seems adequate for HAL absorption and conversion to PpIX in submucosal inflammatory and epithelial cells and can be used in a PDT trial of GELP.