Evaluation of time-dependent response to psoralen plus UVA (PUVA) treatment with topical 8-methoxypsoralen (8-MOP) gel in palmoplantar dermatoses

BACKGROUND: Topical psoralen plus UVA (PUVA) is an effective treatment for localized forms of eczema, psoriasis, and palmoplantar pustulosis, which avoids some of the undesirable side-effects of systemic psoralens. Aims In this study, the efficacy of topical PUVA treatment with 8-methoxypsoralen (8-MOP) gel was compared with placebo plus UVA in chronic recurrent palmoplantar dermatoses. METHODS: Twenty-two patients with palmoplantar disease (11 with psoriasis vulgaris, six with eczema, and five with pustulosis) were enrolled in the study. The study design was a left-right comparison: one hand or foot was treated with 8-MOP 0.01% gel plus UVA, whilst the contralateral hand or foot received placebo and UVA for 6 weeks. Twenty minutes after application of the gel, both sides were exposed to UVA. The treatment regimen was three times a week, and the UVA dose was increased weekly by 20%. RESULTS: A comparison of the pre- and post-treatment scores with regard to the severity of the clinical picture and the infiltration of plaques showed a significant decrease (from 7.5 +/- 2.0 to 2.5 +/- 2.1 and from 2.0 +/- 0.7 to 0.3 +/- 0.5, respectively) in the sites treated with 8-MOP gel compared with placebo after 6 weeks. CONCLUSION: The results of the study indicate that at least 18 courses of local PUVA within 6 weeks, with a cumulative dose of 87 J/cm(2), are required to induce a significant decrease in the disease severity and an improvement in the infiltration of plaques due to 8-MOP gel at a concentration of 0.01% when treating chronic recurrent palmoplantar dermatoses.     

Kinetics and dose-response of photosensitivity in cream psoralen plus ultraviolet A photochemotherapy: comparative in vivo studies after topical application of three standard preparations

BACKGROUND: Topical photochemotherapy with bath psoralen plus ultraviolet (UV) A irradiation (PUVA) has been developed to reduce possible side-effects of oral PUVA therapy. Although the efficacy of bath PUVA therapy appears to be similar to oral PUVA therapy, provision of bathing facilities has obvious economic, logistic and sanitary implications. Cream PUVA therapy has recently been developed as a variation of topical PUVA. OBJECTIVES: To understand the photobiological effects and to increase the safety and effectiveness of this novel topical PUVA therapy, we assessed the kinetics and dose-response of phototoxicity of 8-methoxypsoralen (8-MOP) cream in order to develop a treatment schedule for this treatment option. METHODS: Ninety-eight patients (63 men and 35 women) undergoing cream PUVA therapy were studied. The phototoxic properties of topically applied 8-MOP in three different water-in-oil creams as vehicles were assessed. In a dose-response study, four concentrations of 8-MOP cream (0.0006-0.005%) were used for determination of the minimal phototoxic dose (MPD). The kinetics of photosensitization were tested by determination of MPDs after different application times of 8-MOP cream (10, 20, 30 and 60 min). The persistence of phototoxicity was assessed by UVA exposure at defined time intervals after application of 8-MOP cream (0, 30, 60 and 120 min). RESULTS: The concentration required to produce sufficient but not undue photosensitization of the skin was 0.001% 8-MOP. The duration of application leading to the lowest MPD was 30 min. Greatest photosensitization was achieved when UVA irradiation was performed between 0 and 30 min after 8-MOP removal. These findings showed no significant difference between the three vehicles used. CONCLUSIONS: Based on our data we recommend application of 0.001% 8-MOP in a water-in-oil cream for 30 min. Irradiation with UVA should be performed within 30 min after removal of 8-MOP cream, as there is a rapid decrease in photosensitivity thereafter.     

PUVA-gel vs. PUVA-bath therapy for severe recalcitrant palmoplantar dermatoses. A randomized, single-blinded prospective study

BACKGROUND/PURPOSE: In order to avoid unwanted effects of systemic psoralen and ultraviolet A (PUVA) therapy, various topical PUVA treatment modalities have been developed and are being increasingly used. However, up to now very few controlled studies comparing the therapeutic efficacy of different topical photochemotherapy modalities are available. Thus, the aim of our study was to compare the clinical efficacy of conventional PUVA-bath therapy to topical PUVA-gel therapy in patients with recalcitrant dermatoses of the palms and soles. METHODS: Twenty patients with severe palmoplantar dermatoses or localized psoriatic plaques were enrolled in our observer-blinded, randomized half-sided study. The treatment modalities compared were: (i) aqueous 8-methoxypsoralen (8-MOP)-containing gel plus broadband UVA irradiation (PUVA-gel therapy) and (ii) 8-MOP bath of the hands and/or feet plus broadband UVA (PUVA-bath therapy). RESULTS: On the body half, which was randomized to PUVA-gel therapy, the median Area and Severity Index for palmoplantar dermatoses (ASIppd) decreased from 28 (range 6-56) to 1.5 (range 1-37, P = 0.00) after a median 33 (13-49) irradiations compared with a reduction from 26.5 (range 6-52.5) to 1.5 (range 0-38, P = 0.00) for PUVA-bath therapy. Both improvements of ASIppd scores were found to be statistically significant, with no significant difference between PUVA-gel and PUVA-bath therapy. Severe phototoxic reactions such as strong erythema, blistering and/or pain were not observed in any patient. CONCLUSION: PUVA-gel therapy seems to be an effective therapeutic alternative to conventional PUVA-bath therapy in treating localized dermatoses of the palms and soles. The advantage of PUVA-gel therapy is reduced organizational efforts and expenses.     

An intraindividual comparative study of psoralen-UVA erythema induced by bath 8-methoxypsoralen and 4, 5', 8-trimethylpsoralen

BACKGROUND: Limited work has been conducted on the characteristics of topical trimethylpsoralen (TMP) psoralen-UVA (PUVA) erythema. OBJECTIVE: We sought to determine the time-course and dose-response characteristics of erythema induced by topical TMP, and to compare these parameters with those for topical 8-methoxypsoralen (MOP) within patients. METHODS: After photosensitization of one forearm with topical TMP, test sites were exposed to a UVA dose series. The procedure was repeated on the other forearm using 8-MOP solution. Erythema was assessed visually and with a reflectance instrument every 24 hours for 7 days. RESULTS: TMP PUVA erythema followed a similar time course to 8-MOP PUVA erythema. The majority of patients were at maximal erythema at or beyond 96 hours. TMP PUVA had a significantly steeper dose-response curve at 48, 72, and 96 hours compared with 8-MOP PUVA. CONCLUSION: On the basis of these data, the optimal time to read the TMP minimal phototoxic dose is 96 hours. In view of the steeper dose-response curve for TMP PUVA, a lower UVA incremental regimen should be considered compared with that for 8-MOP PUVA.     

PUVA therapy for photosensitive psoriasis

The purpose of this study was to assess the prophylactic effect of oral photochemotherapy with psoralens and UVA (PUVA) on patients with light-sensitive psoriasis. Of fifteen patients with photosensitive psoriasis, ten with a history of polymorphous light eruption (PMLE) slowly developing into psoriasis were treated with trimethylpsoralen (TMP) and UVA. Five patients with no preceding PMLE reaction were similarly treated; two with 8-methoxypsoralen (8-MOP), two with TMP and one in whom 8-MOP was later changed to TMP. Good to excellent results were obtained in 9/10 of the first category and in 3/5 of the second, giving an overall efficacy of 80%. Preexisting psoriatic lesions did not, however, heal during TMP therapy but did so when treated with 8-MOP. The results confirm, for light-sensitive psoriatics, the efficacy of PUVA in photosensitive disorders.     

PUVA erythemal sensitivity depends on plasma psoralen concentration and UVA sensitivity

The variation in erythemal sensitivity of the skin during PUVA therapy with oral 8-methoxypsoralen (8-MOP) was examined by measuring both UVA and PUVA erythemal responses, together with plasma 8-MOP concentration, in 27 patients about to start PUVA therapy for psoriasis. The erythema responses were judged visually, and also measured using a reflectance instrument in order to construct dose-response curves. No significant association was found between the UVA and PUVA minimal erythema responses. The plasma psoralen concentration showed significant association with the slope of the PUVA erythema dose-response curve. The slopes of the UVA and PUVA erythema dose-response curves were significantly associated, and this association became much stronger when allowance was made for plasma psoralen concentration. These results show that erythemal sensitivity during PUVA therapy is related to both plasma psoralen concentration and inherent UVA sensitivity, but that this relationship is not apparent when sensitivity is judged visually as the minimal erythema response. The association between PUVA and UVA erythemal sensitivity suggests a common pathway in the vascular response induced hy UVA radiation, with or without psoralen.     

PUVA-bath photochemotherapy (PUVA-soak therapy) of recalcitrant dermatoses of the palms and soles

PUVA-bath therapy has proven to avoid many side effects associated with oral 8-methoxypsoralen (8-MOP) treatment. In order to investigate the effectiveness of topical PUVA-bath therapy (PUVA-soak therapy) on chronic palmoplantar dermatoses, 30 patients with plaque-type psoriasis, pustular psoriasis, endogenous eczema, dyshidrotic eczema and hyperkeratotic dermatitis of the palms and soles were treated over 8 weeks with PUVA-soak using 8-MOP. No additional treatment except skin moisturising cream such as unguentum emulsificans aquosum was used during the study period. The single UVA-doses applied ranged from 0.3 to 3.0 J/cm2 (mean single dose of 1.8 J/cm2), with a mean cumulative dose of 48.6 J/cm2 per patient. Altogether 26 of 30 patients responded well within 8 weeks of treatment with 63% of all patients showing a complete remission and 23% showing considerable improvement, as shown by flattening of plaques, decreased scaling and erythema, as well as decreased vesicle and pustule formation. The condition responding best to our therapy was palmoplantar psoriasis followed by atopic eczema. Hyperkeratotic dermatitis displayed the poorest responding rates in this study. Unwanted side effects such as erythema, pain, blistering or patchy hyperpigmentation were not observed in any of the patients. We conclude that PUVA-soak therapy can be highly efficient in the treatment of palmoplantar dermatoses, especially in the management of palmoplantar psoriasis.     

The effect of PUVA on langerhans cells in rat oral epithelium photosensitized with systemic methoxsalen or topical trioxsalen

BACKGROUND/PURPOSE: Ultraviolet-A radiation (UVA) of the oral mucosa after photosensitization with either systemic methoxsalen (8-MOP) or topical trioxsalen (TMP), i.e. mouth-PUVA, has been reported to be successful in the treatment of oral lichenoid lesions. In the case of PUVA treatment of skin disorders, local immune suppressive effects have been demonstrated, and the antigen presenting epithelial Langerhans cells (LCs) have been shown to be especially sensitive to ultraviolet treatments. Our aim was to compare the photobiological effects of PUVA in oral mucous membrane (OMM) using topical TMP or systemic 8-MOP photosensitization. METHODS: Rat OMM photosensitized with topical TMP or systemic 8-MOP was treated with PUVA using UVA doses of 1-8 J/cm2. The LCs were demonstrated in epithelial sheets of the treated OMM with ATPase staining. RESULTS: Both treatments caused a sim ilar, dose-dependent depletion of ATPase-positive LCs, with a maximal depletion of 80% or 73% with 8 J/cm2 at 2 days after irradiation as photosensitized with TMP or 8-MOP, respectively. This contrasts with earlier published findings in human skin, where topical TMP is an order of magnitude greater a sensitizer than 8-MOP, and PUVA-induced depletion of LCs occurs maximally 5 days after irradiation. CONCLUSION: The depletion of LCs of rat OMM after PUVA treatment is greater using topical TMP compared to systemic 8-MOP, but the difference is significantly smaller than reported earlier in human skin.     

Oral vs. bath PUVA using 8-methoxypsoralen for chronic palmoplantar eczema

Background: Both oral and bath PUVA with 8-methoxypsoralen (8-MOP) have been shown to be effective in the treatment of chronic palmoplantar eczema. However, most studies were retrospective and did not include longer follow-up periods.
Aim: To compare the therapeutic efficacy, tolerability and duration of remission after oral vs. bath PUVA using 8-MOP in patients with chronic palmoplantar eczema.
Methods: Twenty-nine patients were randomly allocated to treatment with oral or bath PUVA. Treatment was given thrice weekly for a maximum of 20 weeks. The primary outcome measure was the improvement in eczema score at the end of treatment. After clearing patients were followed up until relapse or up to 40 months.
Results: Overall, both PUVA modalities appeared comparably effective. However, after stratifying according to eczema type, significant differences in therapeutic outcome in general as well as in response to the two regimes were found. Dyshidrotic eczema responded better to both treatments ( P =0.048) and remained longer in remission than hyperkeratotic eczema. Hyperkeratotic eczema cleared significantly better with oral than with bath PUVA ( P =0.03).
Conclusion: Oral PUVA is preferable for patients with hyperkeratotic eczema and bath PUVA for patients with dyshidrotic eczema.     

Retrospective long‐term follow‐up in patients with chronic palmoplantar dermatoses after good response to bath PUVA therapy

Background: Numerous studies have confirmed the short‐term effectiveness of 8‐methoxypsoralen bath PUVA therapy in patients with chronic palmoplantar dermatoses; however, little is known about long‐term results. Patients and methods: In this retrospective study we examined the long‐term results in 79 patients (mean age: 48 years) with chronic palmoplantar dermatoses who were treated with bath PUVA three times a week over an 8‐year period. A good clinical response (a reduction of more than 50% of the skin lesions) occurred after a mean of 23 treatments and a mean cumulative UVA dose of 39 J/cm² in 51 patients (65%). In 2007 a questionnaire was sent to these 51 patients to assess the long‐term outcome. Results: With bath PUVA treatment, the best results were found in patients with hyperkeratotic eczema (17/22; 77% good clinical response) followed by patients with palmoplantar psoriasis (26/41; 63%) and patients with dyshidrotic eczema (8/16; 50%). Thirty‐four patients (67%) answered the questionnaire after a mean follow‐up interval of 4.3 years (10–87 months). Among these patients, 36% reported an improved course of disease after PUVA therapy with reduced frequency and/or intensity of the skin rash, and 29% of patients reported continued complete clearance. 79% of our patients reported a long‐term reduction in the use of topical corticosteroids during the follow‐up period (mean: 4.3 years). In addition, 67% of patients reported a lasting improvement in quality of life. Conclusions: These data show that bath PUVA may have a long‐term, beneficial influence on the course of disease in a majority of patients with recalcitrant chronic palmoplantar dermatoses.     

Treatment of persistent severe atopic dermatitis in 113 Japanese patients with oral psoralen photo-chemotherapy

Oral administration of psoralen and whole body exposure to UVA (oral PUVA) has been used for the treatment of 113 patients with severe atopic dermatitis (AD). 8-Methoxypsoralen (8-MOP) was given at a dose of 0.5-0.6 mg/kg two hours prior to UVA (3-8 J/cm2) irradiation. Patients were treated three times a week while hospitalized. Other medications which had been given before PUVA therapy were permitted. At four and eight weeks after PUVA therapy, the severity score of AD had decreased by 51% and 80%, and the cumulative doses of UVA were 51.2 J/cm2 and 115.3 J/cm2, respectively. The amounts and strength of topical cortico-steroids were decreased during PUVA therapy. No adverse effects that required discontinuation of the PUVA therapy were observed. After discharge, maintenance therapy with UVB phototherapy and/or conventional treatment of AD kept the patients in remission in the outpatient clinic. The QOL of patients was greatly improved. Photochemotherapy with oral 8-MOP can be indicated in patients with severe, widespread AD, especially if standard therapy fails. This is the first report of oral PUVA therapy in a large series of Japanese patients with AD.     

Narrowband UVB as an effective substitute for psoralen plus UVA: lessons from a psoralen shortage

From March to August 2010, there was a shortage of encapsulated liquid 8-methoxypsoralen (8-MOP), the psoralen used for bath psoralen plus UVA (PUVA) in Toronto, Canada. Patients were forced to discontinue bath PUVA treatment and were transitioned to other therapeutic modalities, including narrowband UVB (nbUVB). A retrospective chart review was conducted of all patients who discontinued bath PUVA due to the unavailability of 8-MOP, with a focus on those who were switched to nbUVB. Sixty-three patients discontinued PUVA, 39 of whom were switched to nbUVB. Fifteen of 17 patients with mycosis fungoides (MF) who were switched to nbUVB improved, and patients with earlier-stage disease were more likely to improve. Ten of 13 (77%) psoriasis patients improved with nbUVB, including two patients whose psoriasis cleared completely. All three small-plaque parapsoriasis patients who switched to nbUVB had complete clearance of their lesions. In conclusion, nbUVB may be a suitable alternative for patients with MF, small-plaque parapsoriasis and psoriasis who cannot access PUVA therapy.     

Topical vitamin D3 derivatives in treating hyperkeratotic palmoplantar eczema: a report of five patients

The treatment of hyperkeratotic palmoplantar eczema is notoriously difficult. A considerable number of patients do not or only partially respond to the current treatments such as topical corticosteroids, topical keratolytics, or PUVA therapy. The purpose of this pilot study was to look for an alternative treatment for hyperkeratotic palmoplantar eczema. We treated five patients with topical vitamin D3 derivatives (calcipotriol 50 microg/g and maxacalcitol 25 microg/g ointments). The lesions almost disappeared after 2 to 8 weeks of treatment in four patients and extremely improved with a seven week treatment in one patient. No adverse effect was observed during or after the treatment, and routine laboratory investigations were within normal ranges. When relapses occurred, they responded well to retreatment. Although the study is preliminary, the results suggest that vitamin D3 derivatives offer a safe, effective alternative form of treatment for recalcitrant hyperkeratotic palmoplantar eczema.     

Bath-water PUVA therapy with 8-methoxypsoralen in mycosis fungoides

PUVA therapy is widely used for early stage mycosis fungoides. While the efficacy of PUVA with oral 8-methoxypsoralen (8-MOP) is well documented, the use of its topical variation, bath-water PUVA therapy with 8-MOP has not been studied. The purpose of this study was to assess the effect of 8-MOP bath-water PUVA therapy in adult patients with early stage mycosis fungoides. We retrospectively evaluated the outcomes of bath-water delivery of 8-MOP (1 mg l(-1)) in 16 patients with early stage mycosis fungoides. In all patients complete response was achieved after a mean duration of 63 days requiring 29 treatments and a mean cumulative UVA dose of 33 J cm(-2). The time to relapse after complete clinical clearance was 45.6 (+/-9.2) weeks. In comparison, oral PUVA therapy with 8-MOP resulted in complete response after 64.5 days (25.8 treatments) with a mean relapse-free period of 30 (+/-3.5) weeks. We conclude that bath-water PUVA therapy with 8-MOP is a valuable photo-therapeutic alternative, which should be considered for patients in whom systemic psoralen cannot be used.     

Psoralen cream plus ultraviolet A photochemotherapy (PUVA cream): our experience

BACKGROUND: Psoralen ultraviolet A (PUVA) bath photochemotherapy has been proved highly effective in the treatment of various dermatoses without potential side-effects of systemic therapy. Another form of topical PUVA therapy (PUVA cream) without the logistical requirements for bath tubs has recently been developed. OBJECTIVE: We sought to develop preparation and treatment standards to PUVA cream and to confirm its clinical efficacy in the treatment of various dermatoses. METHODS: In the first phase, the safety of a novel cream containing 0.002% 8-methoxypsoralen (8-MOP) was determined in six healthy volunteers. In a second phase, 40 patients with different dermatoses were treated with a minor concentration (0.001% 8-MOP), following the guidelines for topical PUVA of the British Photodermatology Group. RESULTS: Plasma levels of psoralen after the application of the novel cream containing 0.002% 8-MOP, were less than 34 ng/mL, the maximum 8-MOP concentration reported for topical PUVA. With a minor concentration (0.001% 8-MOP), important improvement or healing was found in 53.3% of the cycles, generally with a good response since the first month of treatment. Only mild side-effects were detected in 14 patients. CONCLUSIONS: Based on our data, PUVA cream photochemotherapy is well accepted by patients and may be a highly effective treatment even if previous therapy was unsuccessful. In addition, PUVA cream is easier to use than PUVA bath.     

Topical 8-methoxypsoralen photochemotherapy of psoriasis: a clinical study

Topical psoralen plus UV-A irradiation (topical PUVA) was re-evaluated with regard to the timing of UV-A exposure. Symmetrical lesions of fifteen patients with psoriasis were treated with topical PUVA. One side was exposed to UV-A 2 h after topical application of I% 8-methoxypsoralen (2-h interval therapy), while the other side was exposed to the same dose of UV-A within 5 min of the topical application (non-interval therapy). Both regimens were effective. The non-interval therapy was preferred in one case, the 2-hour interval was preferred in three cases, and there was no clear difference in the other eleven cases. There was less tendency to burning with the non-interval therapy, and our study suggests that this is a useful regimen in the out-patient treatment of psoriasis.     

Comparison of the relative therapeutic efficacy of 7-methyl pyridopsoralen and 8-methoxypsoralen in photochemotherapy in psoriasis treatment

A newly-synthesized, monofunctional psoralen derivative, 7-methyl pyrido (3,4-C) psoralen (MPP) was compared with 8-methoxypsoralen (8MOP) with respect to their therapeutic efficacy in photochemotherapy of psoriasis. Psoriatic lesions of six patients were treated with topical application of MPP plus UVA (MPP PUVA) or with 8MOP plus UVA (8MOP PUVA). The UVA doses used in each treatment were 7.5 or 10 J/cm² with MPP and from 1.2 to 3.6 J/cm² with 8MOP. In every patient, marked improvement was observed after 2 to 6 treatments with MPP PUVA or 8MOP PUVA. Three patients showed clearance of each psoriatic lesion treated 9 to 17 times with MPP or 8MOP PUVA. Althought MPP required much higher UVA doses than 8MOP, MPP PUVA was as effective as 8MOP PUVA in treating psoriasis. When irradiating with identical doses of UVA, MPP PUVA appeared to be less active than 8MOP PUVA. None of the patients developed any severe dermatitis reactions during 20 exposures to MPP PUVA, indicating that the probability of inducing allergic contact and photocontact dermatitis may be extremely low. Erythemogenic and pigmentogenic activities of MPP and 8MOP were also compared. The data demonstrated that 8MOP is more than 8 times as effective as MPP for both activities. With the UV doses used in this study, however, every patient produced marked pigmentation after MPP PUVA therapy. Finally, the UVA dose-dependency of MPP PUVA was studied with an additional patient. Both therapeutic and pigmentogenic effects increased as a function of the UVA dose; it appeared impossible to clear psoriasis without producing pigmentation.     

Hand and foot PUVA soaks: An audit of the Massachusetts General Hospital''s experience from 1994 to 1998

Palmoplantar psoriasis and eczema can be chronic recalcitrant dermatoses. Oral psoralen plus ultraviolet A (PUVA) has proven effective for these, but has a number of unwanted side effects. Previous studies have shown that regional PUVA therapy using the 8-methoxypsoralen (8-MOP) soak method followed by immediate UVA irradiation is also beneficial and well tolerated. The purpose of this audit was to determine the efficacy of hand and foot PUVA soaks by reviewing the experience of the Massachusetts General Hospital's Phototherapy Unit with this treatment modality. Phototherapy records of all patients who underwent hand and foot PUVA soaks from 1994 to 1998 were reviewed. Details regarding the treatment procedure, patient compliance, patient response and incidence of side effects were noted and summarized. Of the 56 patients who underwent at least 20 treatments, 29% had excellent response, 42% had minimal to moderate response, and 29% had poor response. The average number of treatments to induce clearing was 41. The average maximum treatment dose at clearing was 5.85 J/cm2, while the average cumulative dose to achieve clearing was 267.17 J/cm2. 8-MOP PUVA soak therapy is quite useful for chronic hand and foot dermatoses. Patient compliance must be emphasized to obtain favorable results.     

Treatment of palmoplantar psoriasis with monochromatic excimer light (308-nm) versus cream PUVA

Palmoplantar psoriasis is a chronic disease, which is very resistant to treatment and often leads to severe disabilities. Photochemotherapy employing psoralens combined with UVA irradiation (PUVA) is a well-accepted therapy for palmoplantar psoriasis. Its topical application (bath PUVA; cream PUVA) avoids the typical side effects of orally applied psoralens. We compared the efficacy of cream PUVA therapy with monochromatic excimer light therapy, a treatment modality employing 308-nm UVB radiation generated by a new kind of light source. Ten patients with psoriasis of the palms and soles were randomly assigned to receive cream PUVA on one side and 308-nm UVB on the contralateral side. Based on the psoriasis area and severity index (PASI) score, clinical assessment was carried out before and 5 weeks after the beginning of the study. At the end of the treatment period both test groups showed a remarkable PASI score reduction (308-nm UVB, 63.57%; cream PUVA, 64.64%). No relevant adverse effects were observed, except for mild irritation in a few patients. After a 12-week follow-up, a relapse of the disease was only observed in one patient. Thus, mono-chromatic excimer light cleared palmoplantar psoriasis as rapidly as cream PUVA. In contrast to cream PUVA, monochromatic excimer light therapy is not associated with prior drug application. This might lead to a lower incidence of adverse reactions and better compliance. Therefore, monochromatic excimer light therapy seems to be a useful new therapeutic option for palmoplantar psoriasis.     

PUVA-induced lymphocyte apoptosis: Mechanism of action in psoriasis

Psoralen plus ultraviolet A (PUVA), utilizing oral 8-methoxypsoralen (8-MOP), is a widely utilized and effective treatment for psoriasis vulgaris. Previous studies have suggested that PUVA's mechanism of action in psoriasis is a result of its direct lymphotoxic effects. Trimethylpsoralen (TMP), a potentially safer compound, has been found to be effective in psoriasis during bath water delivery. In this study we examined the relative anti-lymphocytic effects of TMP and 8-MOP through both flow cytometry and tissue analysis on lesional skin during clinical treatment. Based on FACS analysis on phytohemagglutinin-activated lymphocytes, we found TMP to be nearly 10,000 fold more lymphotoxic compared to 8-MOP. In addition, lymphocytes treated with 8-MOP or TMP with UVA displayed DNA degradation patterns typical of apoptotic cell death. These findings were consistent with our investigation of treated psoriatic skin, with virtual elimination of epidermal CD3+ T-cells following bath water treatment with TMP or 8-MOP. These results support the theory that the therapeutic effects of PUVA stem from its toxic effects on activated lymphocytes. If further investigation supports TMP's lack of carcinogenicity, this potent lymphotoxic treatment may prove to be one of the safest and most effective treatments for psoriasis.