Caracterización clínico-epidemiológica de pacientes con daño actínico crónico. Cochabamba, Bolivia / Clinical-epidemiological characterization of patients with chronic actinic damage. Cochabamba, Bolivia

RESUMEN Introducción: el daño actínico crónico es un grupo de alteraciones en la estructura, función y apariencia de la piel como resultado de la exposición no controlada a las radiaciones ultravioletas. Puede provocar el cáncer de piel. Objetivo: caracterizar a los pacientes con daño actínico crónico, atendidos en la consulta de Dermatología del Hospital Comunitario Valle Hermoso, en el departamento de Cochabamba, Bolivia. Materiales y métodos: se realizó un estudio clínico descriptivo, prospectivo, en un universo de 1 833 pacientes diagnosticados con daño actínico crónico, atendidos en la consulta de Dermatología del Hospital Comunitario Valle Hermoso, en Cochabamba, entre septiembre de 2017 y septiembre de 2018. Se evaluaron las variables edad, sexo, color y fototipo de piel, ocupación, uso de medios de protección solar, exposición a otro tipo de radiaciones, manifestaciones clínicas de fotodaño y altitud del lugar de residencia. Resultados: predominaron el grupo de edad de 25 a 59 años, el sexo femenino, el color de piel mestizo (77,08 %), el fototipo de piel IV (76,98 %) y la ocupación comerciante (72,56 %). La mayoría de los pacientes (82,7 %) no utilizaron medios de protección solar, y el 99,8 % no tuvieron exposición a otro tipo de radiaciones. Las lesiones por fotodaño que prevalecieron fueron melasma (83,03 %) y lentigos (12,22 %). El 99,29 % vivían en zonas de gran altitud. Conclusiones: se caracterizaron los pacientes con daño actínico crónico, obteniendo en algunas variables estudiadas resultados similares a los mencionados por otros investigadores (AU).

ABSTRACT Introduction: chronic actinic damage is a group of alterations in the structure, function, and appearance of the skin as a result of uncontrolled exposure to ultraviolet radiation. It can cause skin cancer. Objective: to characterize the patients with chronic actinic damage, treated at the Dermatology consultation of Valle Hermoso Community Hospital, in the department of Cochabamba, Bolivia. Materials and methods: a descriptive, prospective clinical study was conducted in a universe of 1,833 patients diagnosed with chronic actinic damage, treated at the Dermatology clinic of the Valle Hermoso Community Hospital, Cochabamba, between September 2017 and September 2018. The variables age, sex, skin color, skin phototype, occupation, use of sun protectors, exposure to other types of radiation, clinical manifestations of photodamage and altitude of the place of residence were evaluated. Results: the age group from 25 to 59 years, the female sex, mestizo skin color (77.08 %), the IV skin phototype (76.98 %) and merchant occupation (72.56 %) predominated. Most patients (82.7 %) did not use sun protection means, and 99.8 % had no other radiation exposure. The prevailing photodamage lesions were melasma (83.03 %) and lentigo (12.22 %). 99.29 % lived in high altitude areas. Conclusions: the patients with chronic actinic damage were characterized, obtaining in some variables studied results similar to those mentioned by other researchers (AU).

Clinical features of genetic cutaneous porphyrias in Israel: A nationwide survey.

BACKGROUND: There are three major types of genetic cutaneous porphyrias (GCP): erythropoietic protoporphyria (EPP), variegate porphyria (VP), and hereditary coproporphyria (HCP). Scarce data are available regarding their impact on patients' quality of life in the Mediterranean region. PURPOSE: To describe the cutaneous features of GCP in Israel. METHODS: An established nationwide cohort of patients with GCP diagnosed during 1988-2019 was surveyed by telephone for cutaneous features of GCP. Impact on quality of life was assessed using the Dermatology Life Quality Index. RESULTS: Of the 95 patients with GCP, 71 (75%) completed the survey (21 HCP; 40 VP; 10 EPP). All EPP patients reported cutaneous symptoms compared with 58% of VP and 5% of HCP (P < .001). Mean age at symptom onset was 7 ± 6 years in EPP and 25 ± 15 years in VP (P < .001). Photosensitivity was the most common symptom in EPP (90%). In VP photosensitivity (52%), blistering (52%) and scarring (74%) were all common symptoms. In both VP and EPP, the dorsal hands/forearms were the most affected regions (≥96%), and in ≥ 78%, symptoms occurred on an almost daily basis. All EPP patients changed their lifestyle due to cutaneous symptoms vs 57% in VP. Major effect on quality of life was observed among EPP patients compared with a moderate effect in VP. No treatment was effective in EPP, while phototherapy and moisturizers were effective in 5 of 7 (71%) VP patients. CONCLUSION: This study sheds light on the cutaneous features of the GCP, which have a substantial effect on patients' quality of life.

Frequency of occurrence of polymorphic light eruption in patients treated with photohardening and patients treated with phototherapy for other diseases.

BACKGROUND: Medical phototherapy can lead to the manifestation of polymorphic light eruption (PLE), though little is known about the frequency of such events. AIMS: The aim of this Austrian single center study was to retrospectively investigate over a 4-year time period the frequency of PLE in patients prone to the condition and patients with other diseases under phototherapy (mainly narrow-band and broad-band UVB). MATERIALS AND METHODS: The data for analysis were obtained from the electronic health and patient record database and patient files of the Photodermatology Unit, Department of Dermatology, Medical University of Graz, Austria. RESULTS: PLE occurred in 24.3% (18/74) of PLE patients but only 0.7% (3/421) of psoriasis patients under phototherapy (chi-square; P < 0.0001). PLE also occurred in 1.2% (3/257) of patients with atopic eczema, 0.8% (1/118) with prurigo, 3.5% (4/115, P = 0.0206) with parapsoriasis en plaques/mycosis fungoides, 7.4% (2/27, P = 0.0013) with granuloma anulare, 14.3% (1/7, P = 0.0002) with scleroderma, and 16.7% (1/6, P < 0.0001 vs. psoriasis) with pityriasis lichenoides chronica or pityriasis lichenoides eruptiva et varioliformis acuta. DISCUSSION AND CONCLUSION: These results are helpful for treatment allocation and risk estimation of PLE occurrence with regard to obtaining informed consent not only from PLE-prone patients but also from patients with other skin disorders commonly treated by phototherapy.

Solar urticaria: Epidemiology and clinical phenotypes in a Spanish series of 224 patients. / Urticaria solar. Epidemiología y fenotipos clínicos en una serie española de 224 pacientes.

BACKGROUND: Solar urticaria is a chronic inducible urticaria also classified as an idiopathic dermatosis. The objective of this paper is to define the phenotypic characteristics of solar urticaria and to evaluate its incidence. MATERIAL AND METHOD: This was a retrospective multicenter study in which data were gathered on the epidemiology and clinical, photobiologic, laboratory, and therapeutic characteristics of solar urticaria. RESULTS: A total of 224 patients (141 women and 83 men) were included from 9 photobiology units. The mean age of the patients was 37.9 years (range, 3-73 years). A history of atopy was detected in 26.7%, and the most common presentation was allergic rhinitis (16.5%). Clinical signs were limited to sun-exposed areas in 75.9% of patients. The light spectrum most commonly implicated was visible light only (31.7%), and in 21% of cases it was only possible to trigger solar urticaria with natural light. The treatments most widely used by photobiology experts were oral antihistamines (65.46%), followed by different forms of phototherapy (34%). Complete resolution was observed most often in patients with solar urticaria triggered exclusively by visible or natural light, with statistically significant differences with respect to other wavelengths (P<.05). No increase in the annual incidence of solar urticaria was observed. CONCLUSIONS: We have presented the largest series of solar urticaria published to date. The epidemiological, clinical, and photobiologic findings confirm previously reported data, although there was a particularly high rate of negative phototests in our series. Reactivity exclusively to visible or natural light was associated with a higher probability of resolution. No increasing trend was observed in the annual incidence.

Influence of meteorological data on sun tolerance in patients with erythropoietic protoporphyria in France.

BACKGROUND: Erythropoietic protoporphyria (EPP) is a rare metabolic disorder, characterized by photosensitivity, caused by errors of the haem biosynthetic pathway. Avoidance of sun exposure is recommended; however, some patients suggested a paradoxical improvement of symptoms when they move to sunny areas. OBJECTIVES: In a national French study, we sought to investigate the influence of sun exposure on EPP symptoms. MATERIALS AND METHODS: We used a national transversal observational study by questionnaire. Patients were selected from the national record of the Centre Français des Porphyries (French Porphyrias referral centre). Sun exposure level by geographic area was assessed using climate data provided by the French national meteorological service (Météo France). RESULTS: Eighty-nine patients were included. We notably observed that 40% of patients declared an improvement in their tolerance of sun exposure after repeated sun exposures. In the more sunny areas, the intensity of the pain was lower (r = -0·26) and the duration of the sun exposure responsible for flares was longer (r = 0·39) than in the areas that were less sunny (P < 0·05). CONCLUSIONS: This study proposes a benefit of natural progressive sun exposure for patients with EPP.

Drug-induced photosensitivity.

Drug-induced photosensitivity is common. The principal mechanism of systemic drug photosensitivity is phototoxicity and the principal mechanism of topical drug photosensitivity is photoallergy. Photopatch testing is helpful to determine suspected topical agent photoallergies (eg, from ultraviolet filters in sunscreens) but generally not helpful in detecting systemic drug photosensitivity. Drug-induced photosensitivity is usually best managed by stopping the suspected drug. Other measures, including phototherapy using wavelengths that do not elicit the response, are sometimes necessary.

Erythropoietic protoporphyria in Sweden: demographic, clinical, biochemical and genetic characteristics.

OBJECTIVE: To investigate the demographic, clinical, biochemical and genotypic features of patients with erythropoietic protoporphyria (EPP) in a Swedish cohort. DESIGN: Cross-sectional questionnaire, biochemical and genetic study. SETTING: Sweden. SUBJECTS: Fifty-one Swedish individuals known in 2008 to have EPP confirmed by molecular diagnosis. There were no exclusion criteria; all patients were included in the demographic and genetic study. A total of 92% participants completed the questionnaire study and 82% the biochemical study. RESULTS: The prevalence of EPP was 1 : 180,000. Nine novel ferrochelatase gene mutations were found. The most commonly reported age at onset of symptoms was the first year of life and the mean age at diagnosis was 22 years. Painful photosensitivity was the main symptom. Exogenous factors other than sunlight were frequently reported to cause cutaneous symptoms. One in five patients reported a positive effect of beta-carotene therapy. A marked impact of EPP on quality of life was reported. Women had a significantly lower mean erythrocyte protoporphyrin concentration than men. Of all participants, 84% had insufficient vitamin D concentrations, 44% had below normal serum ferritin or transferrin saturation levels and red cell abnormalities were common. CONCLUSIONS: The notably delayed diagnosis suggests the need for an increased awareness of EPP. Disturbed erythropoiesis, biochemical signs of iron deficiency and low vitamin D levels are frequent findings in this disease. New and better treatments are needed as current treatment options for symptom amelioration are limited. Vitamin D supplementation should be considered.

Diagnosis and pharmacological treatment of chronic actinic dermatitis in the elderly: an update.

Chronic actinic dermatitis (CAD) describes a condition resulting from abnormal photosensitivity; the dermatitis is clinically similar to contact allergic dermatitis. Sun-exposed skin is more commonly affected but the condition can extend to and encompass unexposed skin. CAD is relatively rare but becomes more prevalent in the elderly population. Phototesting, patch testing and laboratory results should be used to help guide diagnosis. In the elderly, it is important to distinguish CAD from drug-induced photosensitivity. Management of the condition requires sunlight avoidance and use of sunscreens, topical emollients and topical corticosteroids. Oral corticosteroids and immunosuppressive therapy such as azathioprine may be indicated but should be used with caution in the elderly.

Photodermatology. Quo vadis? / Fotodermatología. Quo vadis?

El eritema no fue siempre un buen parámetro para valorar el daño solar y es más difícil de utilizar en fototipos más oscuros. Mientras que en el pasado la fotodermatología estaba centrada en la piel caucásica, el futuro puede ser completamente diferente. Además, el color de la piel no sólo tiene un papel protector, sino también una importancia social; este es otro factor a tener en cuenta. La fotodermatología y la clasificación de las fotodermatosis estarán más globalizadas en el futuro. Los desafíos para la fototerapia serán una reducción del tiempo de irradiación y del número de tratamientos y el desarrollo de fuentes de luz específicas para indicaciones concretas. Las fotopruebas deberán estandarizarse internacionalmente y esto dará lugar a la creciente necesidad de una Sociedad Internacional de Fotodermatología. Hasta ahora, la mayoría de los tratamientos han sido más bien sintomáticos. Hay también más razones para creer que otros tratamientos más activos puedan tener un papel en el futuro (AU)

Erythema was not always a good parameter for acute solar damage and is much more difficult to use in darker skin types. While in the past photodermatology was mainly focused on Caucasian skin, the future, therefore, could be completely different. In addition, skin colour has not only a protective importance but also a social importance. This is another factor that should be taken into account. Photodermatology and the classification of photodermatoses will also become more globalised in the future. Challenges for phototherapy will be a reduction of the irradiation time and the number of treatments, and the development of specific light sources for specific inrucations. Phototesting should be standardised on an international level and this will lead to a growing need for an International Society for Photodermatology. Until now, most treatments have been rather symptomatic. There are also more and more reasons to believe that more active treatments could play a role in the future (AU)

Solar urticaria.

Solar urticaria is a relatively rare immunoglobulin E-mediated photodermatosis that is caused by specific, yet diverse wavelengths of light. The history, epidemiology, clinical manifestations, histology, etiology/pathogenesis, differential diagnosis, treatment, course, and prognosis of solar urticaria are reviewed herein.

Dermatitis de Berloque en la infancia / Childhood Berloque dermatitis

La dermatitis de Berloque es una fotodermatosis que requiere una anamnesis temporal cuidadosa: el antecedente de la aplicación de la sustancia en la superficie corporal y la exposición solar posterior nos dan la clave para su correcto diagnóstico. Aunque habitual para el dermatólogo, no es un cuadro clínico común en el paciente pediátrico y debe incluirse en el diagnostico diferencial de las dermatitis de contacto, incluso en casos de maltrato infantil(AU)

Berloque dermatitis is a photodermatosis that requires a careful examination of the foregoing sequence of events. The application of a substance to some part of the body prior to sun exposure is the key for an accurate diagnosis. Although it is commonly diagnosed by dermatologists, it is unusual among pediatric patients, and should be included in the differential diagnosis of certain forms of contact dermatitis and even cases of child abuse(AU)

[Incidence of drug-induced photosensitization during phototherapy]. / Incidence des accidents par photosensibilisation médicamenteuse au cours des photothérapies.

BACKGROUND: Exogenous photosensitization represents one of the adverse effects of phototherapy. However, the impact of potentially photosensitizing drugs on the incidence of photo-induced eruptions during phototherapy is unknown. AIM OF THE STUDY: To determine the incidence of drug photosensitization during phototherapy. PATIENTS AND METHODS: This was a retrospective study of all patients undergoing phototherapy between November 1999 and April 2004 in the Dermatology Department of Caen University Teaching Hospital. Details of all topical or systemic medications taken before or during phototherapy were recorded. Since methoxsalen induces photosensitization, sessions of phototherapy were stratified according to whether methoxsalen was given. Screening was performed for the following clinical signs of drug photosensitization: acute photo-induced, erythematous and/or vesicular eruption, associated with pruritus or burning. RESULTS: In the non-methoxsalen group, use of a potentially photosensitizing drug was found for 29/155 TL01 phototherapy sessions. Drug-induced photosensitization was suspected in 3/29 sessions (10.3%). In the methoxsalen group, a potentially photosensitizing drug was found in 21/118 sessions of PUVA-therapy. Drug-induced photosensitization was suspected in 4/21 sessions (19%). Risk of photo-induced eruption was not associated with photosensitizing drug therapy, TL01 phototherapy or PUVA-therapy. DISCUSSION: Drug photosensitization appears to be rare during phototherapy, regardless of photosensitizing drug intake. It is twice as frequent during PUVA-therapy as during TL01 phototherapy but this difference is not significant.

The difference between the constitutive and facultative skin color does not reflect skin phototype in Asian skin.

BACKGROUND/PURPOSE: The assessment of the sensitivity of human skin to ultraviolet (UV) radiation is important in the area of phototherapy, photodermatoses, photo-aging, photo-carcinogenesis, and photo-protection. Some reports have shown that quantitatively measured skin color is a good indicator for predicting UV sensitivity to human skin in Caucasians. In this study, our aim was to define the correlation between skin color and the skin phototype assessed by the Fitzpatrick method in Asian brown skin. METHODS: A total of 180 medical students with similar life styles were included in this study. Their skin phototype was classified according to the system introduced by Fitzpatrick. Then, using a Minolta Spectrophotometer CM-2002, their skin color was determined on the buttocks and forehead. The buttock color was taken as the constitutive skin color, and the forehead color as the facultative skin color. Using these measured values, we compared the skin color with the skin phototype to find their correlation. Also, we investigated whether the difference between the constitutive and facultative skin colors of each individual had a relationship with his or her skin phototype. RESULTS: The constitutive skin color became darker with increasing skin phototype, and this change was statistically significant. As for the facultative skin color, it also became darker with increasing skin phototype, but was less well correlated with the skin phototype than the constitutive skin color. However, the difference between the constitutive and facultative skin colors did not show consistent results in predicting the skin phototype. CONCLUSION: In this study, we found that the constitutive skin color can be a good indicator of the skin phototype. However, the difference between the constitutive and facultative skin colors of each individual does not give any meaningful information for the assessment of his or her skin phototype in Asian skin.

Curso clínico de la erupción polimorfa lumínica con medidas de fotoprotección con categoría ULTRA / Evolution of polymorphic light eruption using category ULTRA photoprotective measures

La erupción polimorfa lumínica (EPL) es la fotodermatosis idiopática más común. Suele presentarse en primavera y se caracteriza por la aparición de lesiones pruriginosas de diferente morfología en las zonas expuestas al sol. Aunque existen distintos tratamientos, se considera que la mejor medida consiste en restringir la exposición y utilizar fotoprotectores del factor alto. En este estudio epidemiológico se han evaluado las características clínicas y la revolución de la EPL con medidas de fotoprotección con categoría ULTRA (FPS 90) durante tres meses es una muestra de 26 pacientes. La gravedad de los síntomas y la intensidad de prurito disminuyeron significativamente en tan sólo 15 días hasta niveles irrelevantes y siguió disminuyendo hasta el final del estudio. Los resultados sugieren que la utilización del fotoprotector FPS 90 ayuda a la resolución de las lesiones del brote agudi del EPL.

Chronic actinic dermatitis: a retrospective analysis of 44 cases referred to an Australian photobiology clinic.

A retrospective study was performed to analyse the clinical and photobiological features and therapeutic outcomes of 44 patients with chronic actinic dermatitis who were evaluated over an 8.3-year period. The study population comprised 37 men and seven women with a mean age of 62.7 years (range 26-85 years). The most common abnormal phototest results were decreased minimal erythema doses to both UVA and -B (73.8%), and to UVA alone (14.3%). Twenty-six patients (78.8%) had at least one allergic, photoallergic or combined allergic/photoallergic reaction. A total of 139 positive contact or photocontact reactions were recorded (mean 4.2 per patient). Most commonly, treatment consisted of photoprotection, topical corticosteroids and episodic use of systemic agents, in particular azathioprine.

Polymorphic light eruption.

Polymorphic light eruption (PMLE) is the most common photodermatosis. It is typically characterized by nonscarring, pruritic, erythematous papules, plaques, or vesicles on sun-exposed skin that develop 30 minutes to several hours after sun exposure. The eruption may persist for a few hours to as long as 2 weeks. Females are affected two to three times more often than males. PMLE has been reported in all races, but tends to affect fair-skinned individuals with Fitzpatrick skin types I-IV most commonly. The pathogenesis of PMLE has been difficult to define, although it appears to be an immune-mediated delayed-type hypersensitivity reaction. Abnormalities of arachidonic acid metabolism and a possible correlation with lupus are other theories that are reviewed. Treatment options have been explored extensively. While "hardening" or desensitization of the skin through repeated irradiation seems to be the most effective, therapeutic options such as sun avoidance/sun protection, oral carotenoids, and antimalarials are also considered.

Polymorphous light eruption.

Polymorphous light eruption (PLE) is a common idiopathic photosensitivity disorder with an estimated prevalence of 10-20%. It is characterized by an intermittent skin reaction to ultraviolet (UV) radiation exposure, consisting of non-scarring pruritic erythematous papules, vesicles or plaques that develop on light-exposed skin. Despite the different morphology in different individuals, the eruption tends to have a monomorphous presentation in any single subject. The histopathological features of PLE are distinct and comprise a perivascular lymphocytic infiltrate in the dermis, subepidermal oedema and variable epidermal changes. The pathogenesis of PLE is not well known, but findings suggest that it is a delayed-type hypersensitivity reaction to one or more UV-modified cutaneous antigens. The principal action of PLE is mainly in the UVA region, although some subjects exhibit sensitivity to UVB alone or to both UVA and UVB radiation at the same time. Preventive measures in PLE include the regular use of photoprotective methods combined with graduated exposures to natural sunlight. The induction of immune tolerance by phototherapy and photochemotherapy are useful prophylactic methods in moderate to severe cases. The role of systemic agents in the management of PLE is under investigation. This article reviews the epidemiological, pathogenetic and clinical aspects of PLE and discusses recent advances in the diagnostic approach and management of this condition.

Ergotism and photosensitization in swine produced by the combined ingestion of Claviceps purpurea sclerotia and Ammi majus seeds.

Poisoning of domestic animals happens frequently in the southeast of Buenos Aires Province (Argentina). Intoxications are produced mainly by the ingestion of plants and mycotoxins, but animals are rarely affected simultaneously by both types of agents. One herd of pigs suffered simultaneous intoxications by ergot alkaloids from Claviceps purpurea sclerotia and furocoumarins from Ammi majus seeds. Pigs were fed a diet composed of wheat (poor quality) or corn and protein and vitamin supplements. This diet was completed with forage sorghum. Nervous signs were first observed 5-7 days after the initiation of feeding the suspect ration. These signs were followed by cutaneous irritation. Snout ulcers, eyelid edema, and conjunctivitis were observed in several piglets. Ten days after the start of feeding the incriminated ration, 8 abortions were observed. Many of the sows that were nursing piglets developed udder edema and teat cracking. Dermal lesions were observed in most of the animals with unpigmented areas in the skin but not in a Duroc-Jersey boar. Removal of the incriminated diet and feeding of another diet prepared with good-quality wheat allowed all the animals to recover in 15 days. The herd experienced normal pregnancies and parturitions, litter sizes, and piglet weights when fed a cleaned portion of the poor-quality wheat. No photosensitization lesions were observed. Examination of impurities in the suspected wheat indicated the presence of 2.2% of A. majus seeds and 0.14% of C. purpurea sclerotia. The quantitative analysis indicated the presence of 3.2 g xanthotoxin and 0.65 g bergaptene/100 g A. majus seeds and 0.73 g ergot alkaloids (expressed as ergonovine) per 100 g of C. purpurea sclerotia. Qualitative analysis demonstrated the presence of ergotamine, ergocristine, and ergonovine. These results indicate that clinical signs and lesions were caused by the ingestion of large quantities of these biologically active compounds.

Photosensitivity associated with combined UV-B and calcipotriene therapy.

BACKGROUND: Ultraviolet B phototherapy is an effective agent for the treatment of psoriasis; its most frequent acute side effect is burning of the skin. It has been combined with various other topical or systemic agents to augment therapeutic effect. Recently, UV-B therapy has been used with calcipotriene ointment (Dovonex, Westwood-Squibb, Buffalo, NY), a new vitamin D analogue. OBSERVATIONS: We report four cases of chronic plaque psoriasis that developed in patients who used UV-B phototherapy for a substantial period without ill effects and in whom photosensitivity reactions within psoriatic plaques developed after calcipotriene ointment was added, without changes in their UV-B dosage or frequency of treatment. The time from starting calcipotriene therapy to the development of photosensitivity ranged from 4 to 28 days, and the number of UV-B exposures during this period varied between one and 12 treatments. The mean UV-B dose at burning was 1114mJ/cm2. Twenty-two patients had used calcipotriene in combination with UV-B therapy of a total of 103 UV-B-treated patients during the period when the adverse events occurred. Half these patients started calcipotriene therapy prior to starting treatment with UV-B. However, cases of photosensitivity occurred only in the remaining half of the patients in whom calcipotriene therapy was added during UV-B therapy. Combined therapy was able to be continued or resumed in two patients by reduction of the UV-B dose. In three cases, phototesting, confirmed greater photosensitivity to calcipotriene-treated skin than to skin to which hydrated petrolatum was applied. CONCLUSIONS: Calcipotriene ointment should be introduced with caution in patients already receiving UV-B phototherapy, particularly those receiving high doses of UV-B. The mechanism of this photosensitivity reaction is unknown. This increased sensitivity to UV-B may be a result of the effect of calcipotriene on stratum corneum thickness, epidermal melanization, a result of its effect on the inflammatory reaction to UV-B irradiation, or, possibly, because it is a phototoxic agent.