Topical photodynamic therapy using different porphyrin precursors leads to differences in vascular photosensitization and vascular damage in normal mouse skin.

Different distributions of hexyl aminolevulinate (HAL), aminolevulinic acid (ALA) and methyl aminolevulinate (MAL) in the superficial vasculature are not well studied but they are hypothesized to play an important role in topical photodynamic therapy (PDT). The colocalization of fluorescent CD31 and protoporphyrin IX (PpIX) was calculated using confocal microscopy of mouse skin sections to investigate the vascular distribution after topical application. Vascular damage leads to disruption of the normal endothelial adherens junction complex, of which CD144 is an integral component. Therefore, normal CD31 combined with loss of normal fluorescent CD144 staining was visually scored to assess vascular damage. Both the vascular PpIX concentration and the vascular damage were highest for HAL, then ALA and then MAL. Vascular damage in MAL was not different from normal contralateral control skin. This pattern is consistent with literature data on vasoconstriction after PDT, and with the hypothesis that the vasculature plays a role in light fractionation that increases efficacy for HAL and ALA-PDT but not for MAL. These findings indicate that endothelial cells of superficial blood vessels synthesize biologically relevant PpIX concentrations, leading to vascular damage. Such vascular effects are expected to influence the oxygenation of tissue after PDT which can be important for treatment efficacy.

Light fractionation significantly improves the response of superficial basal cell carcinoma to aminolaevulinic acid photodynamic therapy: five-year follow-up of a randomized, prospective trial.

Photodynamic therapy (PDT) using topical porphyrin-precursors is a promising treatment for superficial basal cell carcinoma (sBCC), but it needs further optimization. The aim of this study was to compare 5-year lesion (complete) response rates of sBCC treated with topical aminolaevulinic acid (ALA)-PDT using a single illumination vs. ALA-PDT using a 2-fold illumination scheme. A prospective, randomized study was performed, in which 91 patients with 299 lesions were treated with a 2-fold illumination scheme with 2 light fractions of 20 and 80 J/cm2 delivered 4 and 6 h after a single application of 20% ALA, and 106 patients with 274 lesions were treated with a single illumination of 75 J/cm2 4 h after a single application of 20% ALA. All lesions were treated at a fluence rate of 50 mW/cm2. An interim time to event analysis of complete response (CR) rates at 12 months showed encouraging results, and therefore lesions were followed for 5 years post-therapy. A third group of 50 patients with 172 lesions treated with 2-fold illumination were included after the initial period and analysed separately. The CR rate was significantly greater following the 2-fold illumination than the single illumination (p = 0.0002, log-rank test). Five years after therapy the CR rate after 2-fold illumination was 88%, whereas the CR rate after single illumination was 75%. The CR rate in the third group of lesions, treated with 2-fold illumination was 97% and 88% at 12 months and 5 years after therapy, respectively. Long-term follow-up indicates superior efficacy in sBCC of ALA-PDT with 2-fold illumination compared with ALA-PDT with single illumination.

Difference in pathogenesis between vitiligo vulgaris and halo nevi associated with vitiligo is supported by an HLA association study.

Human leukocyte antigen (HLA) class II associations with two subtypes of vitiligo: vitiligo vulgaris and halo nevi associated with vitiligo were investigated. In previous studies associations between vitiligo and HLA antigens have been reported but these two subtypes have never been taken into account. However from a clinical and histological point of view, a difference in (auto)-immune pathogenesis can be expected. This difference might be reflected in an association with different HLA alleles. Seventy-six unrelated Dutch Caucasians, 40 with vitiligo vulgaris and 36 with halo nevi associated with vitiligo were included. A panel of randomly chosen HLA typed healthy Dutch blood donors (n = 2400) served as control population. HLA-DR and -DQ typing was carried out on blood samples by amplifying genomic DNA using polymerase chain reaction followed by dot blot hybridization with sequence specific oligonucleotides. The main outcome measures were odds ratio (OR), uncorrected P-value (P(u)) and corrected P-value. There were distinct differences in the clinical manifestations between vitiligo vulgaris and halo nevi associated with vitiligo with respect to precipitating factors, extent and progress of the disease and the association with other auto-immune diseases in the two subtypes and their respective first degree family members. Our stratification reveals differences in HLA class II between both subtypes and between subtypes and controls. A case-control association study showed a significant positive association of HLA-DR4 (OR = 2.787, P(u) = 0.0022) and DR53 (OR = 2.249, P(u) = 0.0153) and a negative association of HLA-DR3 (OR = 0.195, P(u) = 0.0024) with vitiligo vulgaris. The group with halo nevi associated with vitiligo did not show these associations, but had a significant negative association with HLA-DR11 (OR = 0.083, P(u) = 0.0067). In conclusion, the differences in HLA association within clinical subtypes of vitiligo support our suggestion that vitiligo vulgaris and halo nevi associated with vitiligo have distinct pathogenic mechanisms.