Daylight-mediated MAL-PDT is an effective, convenient and nearly pain-free treatment for patients with multiple thin AKs. Daylight-mediated PDT procedures were easily performed and 2 h of daylight exposure resulted in uniformly high response rates when conducted in the period from June to October in Nordic countries.

Daylight-mediated PDT of moderate to thick AKs was less effective than daylight-mediated PDT of thin AKs especially in some centres. However, nearly all thicker lesions (grades II and III) were reduced to a lower lesion grade at 3 months after a single treatment of daylight-mediated PDT.

Where and when to perform daylight-PDT depends on the PpIX light dose and outdoor temperature. The PpIX light dose was influenced by the geographical location (latitude), weather condition and time of year. The UV index was not more suitable than temperature and weather to predict if the intensity of daylight would be sufficient for daylight-PDT.

Background Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease defined by recurrent nodules, tunnels and scarring involving the intertriginous regions. Recent next‐generation sequencing (NGS) studies suggest genera such as Prevotella spp., Peptoniphilus spp. and Porphyromonas spp. are associated with chronic and early HS lesions. However, a systematic investigation of the bacterial microbiome in HS tunnels remains unexplored using NGS. Objective We aimed to investigate the bacterial composition of the luminal white gelatinous material found in HS tunnels using NGS. Methods An exploratory study of patients with diagnosis of HS (n = 32) with tunnels. The tunnels were present either in the groin (n = 17) or in the axilla (n = 15). During deroofing of the tunnels, a sterile E‐swab was taken of the luminal gelatinous material. The samples were investigated using NGS targeting 16S ribosomal RNA. Results The skin microbiome was characterized in 32 HS patients. Overall, five microbiome types were identified: Porphyromonas spp. (type I), Corynebacterium spp., (type II), Staphylococcus spp. (type III), Prevotella spp. (type IV) and Acinetobacter spp (type V). Porphyromonas spp. (type I) and Prevotella spp. (IV) were the most frequent genera found the tunnels. Conclusion This study points to a potential association between the presence of certain anaerobic bacteria (Porphyromonas spp., Prevotella spp.) and HS tunnels. It may be speculated that these two genera are associated with the pathogenesis in HS either as drivers or as biomarkers.

Even very low-intensity/dose artificial daylight-mediated PDT of multiple AKs resulted in a response rate of more than 50%. However, to ensure efficacies equivalent to conventional LED-PDT, the treatment should not be conducted on very overcast days.

Leishmaniasis is a vector borne disease transmitted by phlebotomine sandflies. Cutaneous leishmaniasis (CL) predominantly causes skin ulcers but may disseminate. CL may present a therapeutic challenge. The present study reports the case of a 15‐year old boy with CL consisting of a single, ulcer on the leg, resistant to pentavalent antimony, oral fluconazole and topical ketoconazole therapy. Repeated photodynamic therapy using aminolevulinic acid resulted in complete healing of the ulcer, suggesting utility of this approach in resistant cases of CL.

Photodynamic therapy (PDT) is an attractive treatment option for skin diseases such as actinic keratosis, since large skin areas can be treated with high response rates and good cosmetic outcomes. Nevertheless inflammation and pain are still major side effects. The aim of this study was to investigate the extent to which less time-consuming PDT treatment regimens using methyl aminolevulinate (MAL) decrease protoporphyrin IX (PpIX) photobleaching, inflammation and pain. Twenty-four healthy volunteers were treated with 4 different interventions on each forearm. All 8 fields were tape-stripped 10 times. On the right arm MAL was applied for 20, 40, 60 or 180 min, followed by further incubation after wiping off MAL until 180 min after start and then illuminating with red light 180 min after start. On the left arm MAL or vehicle was applied for 30, 60, or 90 min and illuminated immediately after MAL removal. PpIX fluorescence, photobleaching, objective and subjective erythema (as a measure for inflammation), pigmentation and pain were measured. The results showed a significant correlation between incubation time, time until illumination and photobleaching. Furthermore, there was a significant correlation between photobleaching and erythema and also between photobleaching and pain. In conclusion, shorter PDT regimens result in decreased photobleaching and also less inflammation and pain. We hypothesize that a shorter incubation time is important for the optimal specific subcellular distribution of PpIX and to avoid unspecific distribution. We propose a shorter PDT regimen, "Pulse PDT", comprising, for example 30 min incubation with MAL and illumination after 180 min, and we have planned a study of actinic keratosis and "Pulse PDT".

Inflammation and pain are well known adverse-effects in photodynamic therapy (PDT). There is currently a tendency towards introducing lower concentrations of the photosensitizer than used in the standard treatment for various indications. The aim of this study was to investigate whether reduced concentrations of methyl aminolevulinate (MAL) can reduce inflammation (erythema) during PDT treatment. We measured the formation of protoporphyrin IX (PpIX) using fluorescence and monitored both erythema and pain during and after PDT treatment with conventional 16% MAL and threee reduced concentrations of 2, 0.75, and 0.25% in twenty-four healthy volunteers. We found that lowering the MAL concentration reduced PpIX fluorescence and erythema after PDT treatment. There was a strong correlation (R(2) = 0.70) between the PpIX fluorescence and erythema after treatment. A further increase in erythema after PDT was dependent on pre-treatment skin erythema. PpIX fluorescence could explain 70% of the increase in erythema (P < 0.0005). Pain and post-treatment hyperpigmentation can be reduced but not eliminated by limiting the MAL concentration. An efficacy study of PDT with these three reduced concentrations has not been performed.