Cryotherapy is preferable to ablative CO2 laser for the treatment of isolated actinic keratoses of the face and scalp: a randomized clinical trial.

BACKGROUND: Actinic keratosis (AK) may progress to squamous cell carcinoma. In the case of normal or mildly photodamaged skin, lesion-directed treatments are considered valuable options despite poor published evidence of their therapeutic activity. OBJECTIVES: The aim of this single-centre, open-label, prospective, nonsponsored, randomized, controlled clinical trial was to compare CO2 laser ablation with cryotherapy in the treatment of isolated AKs of the face and scalp. PATIENTS AND METHODS: Patients with isolated (≤ 4) AKs of the face and scalp were randomized to receive CO2 laser ablation or cryotherapy. After 90 days, the overall complete remission (CR) rates of patients and lesions were assessed and correlated with thickness grade. RESULTS: Two hundred patients with a total number of 543 AKs were enrolled. The CR rates of lesions after 3 months were 78·2% with cryotherapy and 72·4% with CO2 laser ablation. Thicker lesions were significantly more responsive to cryotherapy (P = 0·034). Seventy-three patients (71·6%) had CR of all lesions 3 months after cryotherapy and 64 (65·3%) after laser ablation. At 12 months after treatment the number of patients with CR was reduced to 53 with cryotherapy and 14 with laser ablation. CONCLUSIONS: The rate of patients and lesions with CR is similar after 3 months, but more patients remain in stable remission for 12 months after cryotherapy. Cryotherapy is more effective for thick lesions. The cosmetic outcome was good or excellent in almost all patients.

Synergism between narrowband ultraviolet B phototherapy and etanercept for the treatment of plaque-type psoriasis.

BACKGROUND: Previous investigations have demonstrated that a combination of etanercept (ETN) and narrowband ultraviolet B (NB-UVB) phototherapy is more effective than ETN alone. However, it is unclear if this combination is more effective than NB-UVB phototherapy alone. OBJECTIVES: To evaluate whether the combination of NB-UVB phototherapy with ETN improves the efficacy of ETN alone in the treatment of moderate-to-severe psoriasis. METHODS: We enrolled 322 consecutive patients with moderate-to-severe plaque-type psoriasis, who were treated with NB-UVB phototherapy as the first-line treatment option. Patients who did not achieve a 75% improvement in Psoriasis Area and Severity Index (PASI 75) were treated with conventional systemic therapies for psoriasis. If they were ineligible for these, they were treated with ETN 50 mg twice weekly. If they did not achieve PASI 75 within 12 weeks, NB-UVB phototherapy was added. RESULTS: PASI 75 was achieved in 262 patients (81.4%) treated with NB-UVB phototherapy. Sixteen patients (5.0%) dropped out for personal reasons and 24 (7.5%) were treated with at least one of the conventional systemic treatments for psoriasis. Twenty patients (6.2%) were treated with ETN. The combination regimen was needed in eight patients (2.5%) with poor response to both phototherapy and ETN alone. All of these patients achieved PASI 75 and three of them had a complete remission after 14.6 ± 3.3 NB-UVB exposures. The combined treatment was well tolerated without acute adverse events. Unfortunately, all of these patients relapsed, with PASI > 10 within 2.8 ± 1.7 months. CONCLUSIONS: The combined treatment has a synergistic effect for clearing plaque-type psoriasis previously unresponsive to ETN and NB-UVB phototherapy alone. The clearance rate is very high in a very short time without short-term adverse effects. However, concerns regarding potential cocarcinogenicity remain. Therefore the number of patients who require, and could benefit from, the combined treatment is likely to be small.

Advances in photodynamic therapy. A review.

Photodynamic therapy (PDT) has been pioneered in dermatology at the beginning of the 20th century. Today, cutaneous treatments are the most common applications of PDT. Originating from cancer therapy, recent developments have widened the therapeutic spectrum, and now PDT indications range from inflammatory disorders to cosmetic applications. With several photosensitizers approved by regulatory agencies around the world, PDT continues demonstrating its inherent versatility. This review concentrates on aminolevulinic acid-based PDT regimens in dermatology. Recent research has helped to enhance the treatment efficacy of PDT and to further exploit its potential. Evolving strategies are being tested at present experimentally that will increase the power and diversity of cutaneous PDT. Ultimately these regimens will affect future development in clinical applications.

A photobiological and photophysical-based study of phototoxicity of two chlorins.

To understand the fundamental determinants of phototoxic efficacy and absorbed photodynamic dose, the triplet state and photobleaching quantum yields in living cells, cellular uptake, intracellular localization, and correlation with cell viability were studied for the two purpurins tin ethyl etiopurpurin 1 (SnET2) and tin octaethylbenzochlorin (SnOEBC) in ovarian cancer cells (OVCAR5). Although the triplet yields of these two photosensitizers were not significantly affected by cellular incorporation, the photobleaching yields were shown to be 3 orders of magnitude higher for cellular-bound sensitizer than for free or albumin-bound photosensitizer and higher for SnET2 than for SnOEBC for all of the cases. The intracellular concentration of SnOEBC was half that of SnET2 after 3 h- and 24 h-incubation times for both 0.1 microM and 1.0 microM incubation concentrations. Despite the lower concentrations of SnOEBC, the phototoxicity of the two photosensitizers was comparable at 1-microM incubation concentration and was up to 10-fold higher for SnOEBC at the lower concentration. The subcellular localization established using confocal microscopy and molecular probes showed that both photosensitizers were primarily lysosomally localized. SnOEBC, however, had an extra-lysosomal, mitochondrial localization component. The photophysical measurements allowed calculation of the intracellular singlet oxygen production, which indicated that the photosensitizer-light dose reciprocity was limited by photobleaching for SnET2 but only minimally for SnOEBC, and this was confirmed through cell-survival studies. Taken together, these data indicate that the critical determinant of differences in phototoxicity between the two molecules was their relative rates of photobleaching and their subcellular localization. The study points to the importance of combining photosensitizer uptake and localization with photophysical measurements in the relevant biological milieu to reasonably interpret and/or predict photosensitization efficacies.

Pegylation of a chlorin(e6) polymer conjugate increases tumor targeting of photosensitizer.

Photodynamic therapy is emerging as a viable modality for the treatment of many cancers. A limiting factor in its use against intracavity tumors such as disseminated ovarian cancer is insufficient selectivity of the photosensitizer for tumor compared with normal tissue. We report on an approach to improve tumor targeting by exploiting differences between cell types and by chemical modification of a photosensitizer conjugate. Attachment of polyethylene glycol (pegylation) to a polyacetylated conjugate between poly-l-lysine and chlorin(e6) increased the relative phototoxicity in vitro toward an ovarian cancer cell line (OVCAR-5) while reducing it toward a macrophage cell line (J774), compared with the nonpegylated conjugate. Surprisingly, the increased phototoxicity of the pegylated conjugate correlated with reduced oxygen consumption. Pegylation also reduced the tendency of the conjugate to aggregate and reduced the consumption of oxygen when the conjugates were illuminated in solution in serum containing medium, suggesting a switch in photochemical mechanism from type II (singlet oxygen) to type I (radicals or electron transfer). Pegylation led to more mitochondrial localization as shown by confocal fluorescence microscopy in OVCAR-5 cells, and, on illumination, produced a switch in cell death mechanism toward apoptosis not seen with J774 cells. Conjugates were injected i.p. into nude mice bearing i.p. OVCAR-5 tumors, and the pegylated conjugate gave higher amounts of photosensitizer in tumor and higher tumor:normal tissue ratios and increased the depth to which the chlorin(e6) penetrated into the peritoneal wall. Taken together, these results suggest that pegylation of a polymer-photosensitizer conjugate improves tumor-targeting and may increase the efficacy of photodynamic therapy for ovarian cancer.

Specificity of ganglioside binding to rat macrophages.

The binding specificity of rat alveolar macrophages (AM phi) for sheep erythrocytes (E) coated with gangliosides GM1, GM2, GM3, GD1a, GD1b or GT1b was analyzed in a rosette assay by studying the inhibitory effect of gangliosides, various carbohydrates, IgG, C3b-like C3, and fibronectin in this assay. The uptake of gangliosides by E was calculated from radioactivity measurements using 3H-labeled gangliosides. The different gangliosides were taken up by E at 37 degrees C to a similar extent. Uptake of 3H-labeled GM2 correlated linearly to its concn in the incubation medium. Erythrocytes pretreated with the same molar concn of GM2, GD1a, GD1b or GT1b were bound to AM phi to the same degree reaching a maximum of about 90% rosette forming cells. A mean of 17.8% AM phi-bound GM3-coated E. Treatment of E with asialo-GM2 (GA2) or GM1 did not induce significant rosette formation. A dose-dependent inhibition of rosette formation was observed when AM phi were preincubated at 0 degree C with GM2, GM3, GD1a, GD1b or GT1b, but not with GM1 or GA2 Of the tested carbohydrates, sialyl-lactose had a strong inhibitory effect, while lactose was completely ineffective. N-acetyl-neuraminic acid, N-glycolyl-neuraminic acid and N-acetyl-galactosamine were slightly inhibitory. A series of other carbohydrates including highly negatively charged compounds, as well as fibronectin, IgG or C3b-like C3 did not show significant inhibition. Our data indicate the expression of a receptor on rat AM phi recognizing carbohydrates containing sialic acid at or near the non-reducing terminus.

Non-melanoma skin cancer, sun exposure and sun protection.

The incidence of skin tumors including squamous cell carcinoma (SCC), and its biological precursor, the actinic keratosis, and basal cell carcinoma (BCC) often named together non-melanoma skin cancer (NMSC) is growing all over the world in people of Caucasian ancestry. A plenty of clinical and epidemiological studies have demonstrated the causal relationship with high cumulative solar dosages and number of sunburns, although the hazard may be different for different tumors according to the modalities of ultraviolet (UV) exposure. BCC is much more strongly related to measures of intermittent ultraviolet exposure (particularly those of childhood or adolescence) than to measures of cumulative exposure. In contrast, SCC is more strongly related to constant or cumulative sun exposure. Photobiological studies have clarified that sunlight and UVB radiation are complete carcinogens for AK and SCC although the relationship with UVA exposure is much less known. Also the likelihood of BCC has been related to either sunburns and high lifetime solar, UVA and UVB cumulative doses but the pathogenetic pathways of both UVB and UVA radiation for BCC development need to be clarified so far. The lack of a complete knowledge of the photocarcinogenic pathways of keratinocytes has contributed to the limited results of solar photoprotection strategies, beside the limitations of the available sunscreens and present EU regulations.

An action spectrum for the elicitation of erythema in skin persistently sensitized by photobound 8-methoxypsoralen.

Human skin can be rendered persistently photosensitive by topical application of aqueous 8-methoxypsoralen (8-MOP) and exposure to a suberythemogenic dose of more than 380 nm radiation. We report an action spectrum for the elicitation of phototoxic erythema induced by a second exposure of skin pretreated in this way. After correction for unsensitized skin erythema this action spectrum resembles the absorption spectrum of the 4',5'-monoadduct of 8-MOP to DNA. This suggests that the monoadduct is the chromophore for erythema elicited by the second irradiation, and supports the DNA crosslink as the crucial photoproduct causing phototoxic erythema due to 8-MOP in human skin.

Ultrastructural changes in PAM cells after photodynamic treatment with delta-aminolevulinic acid-induced porphyrins or photosan.

Photodynamic therapy (PDT) is the combination of a photosensitizing drug (Ps) with light in the presence of oxygen leading to the generation of reactive molecular species and destruction of cancer cells. In this study we compared PDT with two Ps, the hematoporphyrin derivative Photosan (Ph) and delta-aminolevulinic acid (ALA)-induced endogenous protoporphyrin IX, with respect to mitochondrial function and ultrastructural alterations. The effects of PDT were investigated in PAM 212 cells after different Ps incubation times, light doses, and post-treatment periods. Both Ps induced a light dose-dependent impairment of the mitochondrial function with the dose-response curve being steep for ALA and flat for Ph. The prolongation of the incubation time from 4 to 20 h resulted in an increased reduction of mitochondrial activity after ALA PDT but not after Ph PDT. Treatment with an irradiation dose that decreased mitochondrial activity by 50% (IC50) led to early and profound changes of mitochondrial morphology in ALA photosensitized cells, whereas photosensitization with Ph resulted in more pronounced alterations of lysosomes. We conclude that at bioequivalent sublethal PDT exposures of PAM 212 cells, ALA-induced damage is primarily restricted to mitochondria, whereas Ph-induced cytotoxicity is mediated by damage of the lysosomal system.

Phototherapeutic, photobiologic, and photosensitizing properties of khellin.

Khellin, whose chemical structure closely resembles that of psoralen, is reported to be an efficient drug for treating vitiligo when combined with ultraviolet A irradiation. Photobiological activity on yeast is found to be much lower than that of bifunctional psoralens such as 5-methoxypsoralen. In vitro experiments reveal that khellin is a poor photosensitizer. It behaves as a monofunctional agent with respect to DNA photoaddition. It does not photoinduce cross-links in DNA in vitro or in Chinese hamster cells in vivo. This behavior may explain the low photogenotoxicity in yeast and the lack of phototoxic erythemal response when treating vitiligo with khellin.

Photosensitivity and hyperpigmentation in amiodarone-treated patients: incidence, time course, and recovery.

Amiodarone (AD) induces photosensitivity in 75% of the patients treated with this drug. Phototoxic reactions can be experimentally elicited with UVA but not with UVB. The UVA-MED is significantly reduced after 12 months of treatment. The development of photosensitivity depends on the total dose of AD; 40 g is the minimal cumulative dose requirement. Under the regimens commonly used, photosensitivity can be expected after 4 months of continuous AD treatment and appears to be unrelated to the skin type. Photosensitivity gradually decreases and returns to normal between 4 and 12 months after the withdrawal of AD. AD-related hyperpigmentation develops after an average of 20 months of continuous AD treatment and a minimal total dose of 160 g AD in about 8% of the patients (mainly of skin type I). Electron microscopic examination of the sun-exposed skin of patients without AD discoloration shows pigment deposits similar to those already described in patients with AD hyperpigmentation in exposed and non-exposed skin. Light and electronmicroscopic examination of sun-exposed skin of both clinically photosensitive and non-photosensitive patients reveals perivascular inflammation even in the absence of a clinical rash. Reduplications of vascular basal laminae occur in sun-exposed skin of both patients with and without UVA photosensitivity but are absent from non-exposed skin. In one patient, followed for 33 months after drug withdrawal, massive AD-induced hyperpigmentation was found to be reversible.

Amino acid conjugates of jasmonic acid induce jasmonate-responsive gene expression in barley (Hordeum vulgare L.) leaves.

Leaves of barley (Hordeum vulgare L. cv. Salome) treated with jasmonic acid (JA), its methyl ester (JM), or its amino acid conjugates exhibit up-regulation of specific genes and down-regulation of house-keeping genes. This transcriptional regulation exhibits several specificities. (i) The (-)-enantiomers are more active, and conjugates are mainly active if they carry an L-amino acid moiety. (ii) The various JA-responsive genes respond differentially to enantiomeric and chiralic forms. (iii) Both JA and its amino acid conjugates exhibiting no or negligible interconversion induce/repress genes.

Laser-induced hyperthermia in rat prostate cancer: role of site of tumor implantation.

OBJECTIVES: To investigate the importance of the site of tumor implantation on the treatment response to laser-induced hyperthermia (LIH) of rat prostate cancer (PCa), because interventional manipulations of PCa have been reported to increase metastatic dissemination. METHODS: Seven to nine days after either subcutaneous or orthotopic implantation of MatLyLu cells, LIH (46.5 degrees C) was induced using pulsed irradiations of a neodymium:yttrium-aluminum-garnet laser. Both local control and distant metastases were evaluated. Plasma metalloproteinase 9 (MMP-9) was tested as a possible marker of PCa progression and LIH response. RESULTS: Twelve days after LIH treatment of subcutaneous tumors, the volumes were reduced by 64% after 8 minutes of irradiation, 73% after 10 minutes, 81% after 15 minutes, and 91.1% after 20 minutes. In the orthotopic model, the corresponding tumor reductions were 44% after 10 minutes, 61% after 20 minutes, and 65% after 30 minutes. Lung metastases were observed in only 1 animal with subcutaneous tumors. In contrast, 86% of the orthotopic tumor-bearing animals treated for 30 minutes had lung metastases compared with 23% of the untreated tumor-bearing rats. MMP-9 expression was detected in both orthotopic and subcutaneous tumor tissue and in the plasma of tumor-bearing rats. The prostate tissue of healthy rats and subcutaneous tumor-bearing rats was devoid of MMP-9. The plasma levels of MMP-9 showed a trend toward direct correlation with local tumor control but no correlation with the incidence of metastasis. CONCLUSIONS: These data emphasize the importance of the site of tumor implantation for evaluation of the efficacy of therapeutic interventions and may warrant further studies before widespread clinical application of LIH as monotherapy.

Middermal elastolysis in an elderly man with evidence of elastic fiber phagocytosis.

BACKGROUND: Middermal elastolysis is a clinically and histologically distinct entity. This idiopathic loss of dermal elastic fibers has mostly been reported in younger adults. To our knowledge, the present case, which has been followed up for 4 years, is the first to occur in an elderly man. OBSERVATIONS: Two years after the onset of progressive wrinkling of the upper aspect of the thorax, the patient underwent a biopsy. Histologic examination of the specimens confirmed previous findings of middermal elastolysis. Examination of extracutaneous elastic tissue showed normal findings. Electron microscopy demonstrated elastic fibers embraced by macrophages, which is suggestive of elastic fiber phagocytosis. For the following 4 years, the patient has remained in stable clinical condition. CONCLUSIONS: Middermal elastolysis is probably more common than has been assumed so far. It does not affect nondermal elastic tissue. After progressive loss of dermal elasticity in a circumscribed area, a benign course follows, with a stable condition over several years. Electron microscopic findings indicate that elastic fiber phagocytosis is operative in the disappearance of the middermal elastic tissue.

Long persistence of monofunctional 8-methoxypsoralen-DNA adducts in human skin in vivo.

Human skin can be persistently photosensitized by topical application of aqueous 8-methoxypsoralen plus immediate irradiation with a non-erythemogenic dose of wavelengths above 380 nm. Re-exposure of skin thus sensitized to broadband UV-A produces phototoxic erythema 72-120 h later. The persistence of the photosensitization was demonstrated by phototoxic erythema after re-exposure up to 15 days after the first sensitizing irradiation. According to the concept that the first exposure induces primarily psoralen monoadducts, we consider this an investigation of psoralen monoadduct persistence. In contrast to several earlier studies, this sensitive method indicates that psoralen monoadducts may remain in human skin in vivo for more than 2 weeks after formation.

Scavenger-receptor targeted photodynamic therapy.

Covalent conjugation of a photosensitizer to a ligand that specifically recognized and internalized by a cell-surface receptor may be a way of improving the selectivity of photodynamic therapy (PDT). The class A Type-I scavenger receptor of macrophages, which among other ligands recognizes maleylated serum albumin and has a high capacity is a good candidate for testing this approach. Chlorin(e6) was covalently attached to bovine serum albumin to give conjugates with molar substitution ratios of 1:1 and 3:1 (dye to protein), and these conjugates could then be further modified by maleylation. A novel way of purifying the conjugates by acetone precipitation was developed in order to remove traces of unbound dye that could not be accomplished by size-exclusion chromatography. Conjugates were characterized by polyacrylamide gel electrophoresis and thin-layer chromatography. Photosensitizer uptake was measured by target J774 murine macrophage-like cells and nontarget OVCAR-5 human ovarian cancer cells, and phototoxicity was examined after illumination by a 660 nm diode laser by a tetrazolium assay. All of the purified conjugates were taken up by and after illumination killed J774 cells while there was only small uptake and no phototoxicity toward OVCAR-5 cells. The higher dye:protein ratio and maleylation of the conjugates both produced higher uptakes and lower survival ratios in J774 cells. The uptake and phototoxicity by J774 cells were decreased after incubation at 4 degrees C demonstrating internalization, and confocal microscopy with organelle-specific green fluorescent probes showed largely lysosomal localization. Uptake and phototoxicity by J774 cells could both be competed by addition of the scavenger receptor ligand maleylated albumin. These data show that scavenger receptor-targeted PDT gives a high degree of specificity toward macrophages and may have applications in the treatment of tumors and atherosclerosis.

Lethal photosensitization by endogenous porphyrins of PAM cells--modification by desferrioxamine.

The effects of exogenous delta-aminolevulinic acid (ALA) on cultured PAM 212 cells were investigated. PAM cells exposed to ALA produce an excess of products of the heme biosynthesis pathway within hours. The endogenous porphyrins render the cells photosensitive in a time-, ALA dose- and irradiation-dependent manner. Independently of the ALA-induced photosensitized processes, ALA itself reduces the proliferation rate of PAM cells during the exponential growth phase. Iron deprivation by addition of the chelating agent desferrioxamine (df) accelerates the photosensitizing process, and thus makes it more efficient at lower ALA concentrations. The effects of df were compared with the effects of manganese-df and iron-df. The results indicate that iron trapping is the most important factor for the potentiation of ALA-stimulated photodynamic sensitization as well as for the dark toxicity. Iron complexing agents may thus be used to optimize ALA effects in the photodynamic treatment of cutaneous neoplasms with endogenous porphyrins.

UV-induced unscheduled DNA synthesis in human skin: dose response, correlation with erythema, time course and split dose exposure in vivo.

Unscheduled DNA synthesis (UDS) has been shown to be saturated above a threshold dose of UV-C in human fibroblasts in vitro. We have investigated by autoradiography whether a similar saturation occurs in human skin in vivo with UV-B and whether this phenomenon correlates with the erythemal response. In addition, we determined the time course of UDS at 24 h after exposure and the effect of dual exposures separated by 24 h. The dose-response curve was established by exposure to 1/16, 1/8, 1/4, 1/2, 1, 2, 3, 4 and 6 MEDs UV-B. For the time-course study, areas exposed to 1/2 and 2 MEDs were biopsied after 1, 3, 6, 12 and 24 h. Autoradiography was performed in vitro. The dose-response curve showed a significant increase in UDS from 1/16 to 1 minimal erythema dose (MED), whereas no significant difference was observed between 1 MED and the higher UV-B doses tested. The 24 h time sequence revealed a gradual decrease in UDS activity. The 1/2 MED curve declined more rapidly and reached the zero-level between 12 h and 24 h, whereas about 50% of the initial UDS value was still retained 24 h after 2 MEDs. The dual-dose study revealed that a second hit of fractions of the MED resulted in lower levels of UDS than induced by these fractions alone in previously untreated areas. UDS increases with the erythemal dose between 1/16 and 1 MED. It reaches a plateau after 1 MED and cannot be increased by doses up to 6 MEDs, suggesting a saturation of excision repair in vivo. Time course studies support such a saturation phenomenon. The failure to increase significantly UDS by a second irradiation 24 h after the first exposure needs further clarification. Since persistence of DNA lesions may lead to an accumulation after repeated exposures, additional mechanisms other than excision repair may protect human skin by error-free removal of possibly mutagenic sites. Photoreactivation may be important in this respect.

Investigations of a manganese-containing mimic of superoxide dismutase in riboflavin phototoxicity in human cells in vitro.

The activity and specificity of a manganese-containing low molecular weight mimic of superoxide dismutase (manganese desferioxamine (Mndf)) were investigated in riboflavin (Rf) photosensitization in solution and cell culture. In addition to the very high superoxide dismutase-like activity of Mndf at micromolar concentrations, photochemical studies in solution indicated that it could quench excited singlet and triplet states at millimolar concentrations. Human erythrocytes, human lymphocytes and a human bladder carcinoma cell line were used to evaluate the potential of Mndf for in vivo use. The efficacy and toxicity of Mndf in the protection against Rf photoxicity varied between the different cell types.

Perspectives in cutaneous photodynamic sensitization.

The photodynamic therapy of cutaneous disease is developing more rapidly than that of other organs due to the accessibility of the skin to photosensitizers and light. The use of hematoporphyrin derivative, with its prolonged photosensitivity of normal skin, is gradually being replaced by a new generation of tetrapyrrolic photosensitizers. These are designed to absorb at longer wavelengths for deeper tissue penetration. Many also feature a greatly reduced photosensitizing potential of uninvolved skin. Another major development is the topical and systemic use of aminolevulinic acid for inducing the formation of endogenous porphyrins in cells which result in photosensitivity. This regimen is currently used quite extensively due to the easy availability of both drug and suitable light sources. However, continued investigation of the underlying mechanisms and their regulation will help to improve this specific photodynamic regimen. Currently, researchers use a whole array of therapeutic regimens and schedules for the evaluation of treatment efficacy. A certain uniformity of both treatment parameters and evaluation criteria will help to improve more rapidly our understanding of photodynamic sensitization in skin disease. This will also help us to define the right place and targeting strategies for photodynamic therapy in dermatology.