Kyu Joong Ahn

The relation between the amount of sunscreen applied and the sun protection factor in Asian skin

BACKGROUND The measurement of the sun protection factor (SPF) is the usual method in the examination of the effectiveness of sunscreen. The declared SPF is based on the use of a sunscreen layer of 2 mg/cm(2). However, only around a quarter (0.5 mg/cm(2)) of this amount is generally used in real life. Theoretical calculations have suggested that the effectiveness of SPF is related to sunscreen quantity in an exponential way but this was not confirmed in Asian skin. OBJECTIVES This study was performed to investigate the change in SPF values when less than the recommended amount of sunscreen was applied. METHODS A board divided into 10 areas measuring 7 x 4 cm was placed on the back of 15 healthy volunteers. Low- and high-SPF standard reference sunscreens, and two types of sunscreen (SPF 30 and 35) were each applied on 4 areas, 0.5, 1.0, 1.5, and 2.0 mg/cm(2), respectively, and were left to dry for 20 minutes. The irradiation was conducted at a distance of 50 cm using a template (1 x 1 cm) placed directly on the skin with 10 windows allowing ultraviolet (UV) radiation to pass through with a dose increment of 20%. Erythema was evaluated 20 to 24 hours after exposure to UV radiation. RESULTS Sunscreen showed its expected SPF value when 2.0 mg/cm(2) was applied. The SPF values of the different amounts were significantly different from each other and decreased when less was applied (P < .05). The relation between the amount of sunscreen applied and the SPF provided was most likely to follow exponential growth. LIMITATIONS Spectral differences between our solar simulator and the UV sources of commercial laboratories are likely to be important. In addition, differences in sunscreen application techniques may have influenced the ultimate SPF values. CONCLUSIONS This study concludes that to get the expected SPF value, it is important to apply the UV protective sunscreen precisely in the amount of 2.0 mg/cm(2) on Asian skin as recommended by the Food and Drug Administration. In addition, it was difficult to predict the SPF values when the usual amount of 0.5 mg/cm(2) was applied.

Quantitative investigation on the distribution of Malassezia species on healthy human skin in Korea

This study concerns a culture research based on the data gathered from Korean subjects to examine distribution of Malassezia yeast. Malassezia yeast were cultivated out of samples from scalp, forehead, chest, arm and thigh. Malassezia restricta was recovered more frequently in the teens and young adults, while M. globosa was the predominant species in subjects older than 50 years of age. The population density of Malassezia yeast was significantly higher in the age group (AG) of 21–30 years compared with other AGs (P < 0.05). It was also significantly higher in the chest compared with the forehead, arm and thigh (P < 0.05). The key is to recognise the existence of a difference in the amount and type of Malassezia species in different AGs as well as body areas, which reflects differing skin lipid levels in various AGs and different body areas.

Change of biophysical properties of the skin caused by ultraviolet radiation-induced photodamage in Koreans

Background/purpose: Ultraviolet (UV) irradiation affects the function and complexion of the skin by inducing changes in physical properties through formation of erythema, proliferation of epithelial cells, DNA damage, activation or inactivation of various enzymes and proteins, and free radical formation. In this study, the authors intended to observe the overall course of changes in barrier function and reflectance of the skin induced by photodamage, and healing reaction in the course of time, and alteration of the skin complexion.

The Investigation on the Distribution of Malassezia Yeasts on the Normal Korean Skin by 26S rDNA PCR-RFLP

BACKGROUND Malassezia yeasts are normal flora of the skin that are discovered in 75~98% of health subjects, but since its association with various skin disorders have been known, many studies have been conducted in the distribution of the yeasts. OBJECTIVE To isolate, identify, and classify Malassezia yeasts from the normal human skin of Koreans by using the rapid and accurate molecular biology method (26S rDNA PCR-RFLP) which overcome the limits of morphological and biochemical methods, and to gather a basic database that will show its relation to various skin diseases. METHODS Malassezia yeasts were cultured from clinically healthy human skin using scrub-wash technique at five sites (forehead, cheek, chest, upper arm, and thigh) and swabbing technique at scalp in 160 participants comprised of 80 males and 80 females aged from 0 to 80. Identification of obtained strains were placed into the one of the 11 species by 26S rDNA PCR-RFLP. RESULTS An overall positive culture rate was 62.4% (599/960). As shown in the experiment groups by their age, the positive culture rate was the highest (74.2%) in the age 21~30 and 31~40 (89/120). In the experiment groups by different body areas, the scalp showed the highest positive culture rate of 90% (144/160). On analysis of 26S rDNA PCR-RFLP, M. globosa was the most predominant species in the age 0~10 (32.8%), 11~20 (28.9%), 21~30 (32.3%). M. restricta was identified as predominant species in the age 41~50 (27.9%), 61~70 (31.5%) and 71~80 (24.0%). In the age 31~40 years, M. sympodialis was found to be the most common species (24.6%). According to body site, M. restricta was more frequently recovered in the scalp (56.8%), forehead (39.8%) and cheek (24.0%) and while M. globosa was more frequently recovered in the chest (36.8%). Higher positive culture rates of Malassezia yeasts were shown in male subjects than female counterparts in all body areas except scalp (p<0.05). Especially in this study, M. dermatis, newly isolated Malassezia species from atopic dermatitis patient in Japan, was isolated and identified in 19 cases (1.9%) in healthy subjects. CONCLUSION The key is to recognize the existence of a difference in the type of Malassezia species in different ages as well as body areas, which reflects differing skin lipid levels in various ages and different body areas. Moreover, 26S rDNA PCR-RFLP analysis which was opted in this study could provide a sensitive and rapid identification system for Malassezia species, which may be applied to epidemiological surveys and clinical practice.

Comparison of Nested PCR and RFLP for Identification and Classification of Malassezia Yeasts from Healthy Human Skin

BACKGROUND Malassezia yeasts are normal flora of the skin found in 75~98% of healthy subjects. The accurate identification of the Malassezia species is important for determining the pathogenesis of the Malassezia yeasts with regard to various skin diseases such as Malassezia folliculitis, seborrheic dermatitis, and atopic dermatitis. OBJECTIVE This research was conducted to determine a more accurate and rapid molecular test for the identification and classification of Malassezia yeasts. METHODS We compared the accuracy and efficacy of restriction fragment length polymorphism (RFLP) and the nested polymerase chain reaction (PCR) for the identification of Malassezia yeasts. RESULTS Although both methods demonstrated rapid and reliable results with regard to identification, the nested PCR method was faster. However, 7 different Malassezia species (1.2%) were identified by the nested PCR compared to the RFLP method. CONCLUSION Our results show that RFLP method was relatively more accurate and reliable for the detection of various Malassezia species compared to the nested PCR. But, in the aspect of simplicity and time saving, the latter method has its own advantages. In addition, the 26S rDNA, which was targeted in this study, contains highly conserved base sequences and enough sequence variation for inter-species identification of Malassezia yeasts.

Clinical efficacies of topical agents for the treatment of seborrheic dermatitis of the scalp: A comparative study

Previous studies have shown that topical steroid and shampoo containing zinc pyrithione provide clinical benefits for treatment of scalp seborrheic dermatitis. But the clinical efficacy of topical tacrolimus, a newly developed calcineurin inhibitor on seborrheic dermatitis, is not well investigated yet. We wanted to compare the clinical efficacy of topical tacrolimus with that of conventional treatment (zinc pyrithione shampoo and topical betamethasone) for treatment of seborrheic dermatitis of the scalp. Patients with seborrheic dermatitis of the scalp were randomly allocated to receive topical betamethasone, topical tacrolimus or zinc pyrithione shampoo. Some patients were instructed to continue the treatments for 8 weeks and the others to discontinue the treatments at week 4. We evaluated the efficacy using a clinical severity score, dandruff score and sebum secretion at baseline, week 4 and week 8. All treatment groups showed significant improvements in clinical assessment after 4 weeks. While the patients treated by zinc pyrithione improved continuously even after cessation of the treatment, the patients treated by betamethasone lotion or tacrolimus ointment were aggravated clinically. Topical tacrolimus was as effective as topical betamethasone, and showed more prolonged remission than topical betamethasone. To treat seborrheic dermatitis of the scalp, we think that the combination therapy of topical steroid or topical tacrolimus, and zinc pyrithione is recommended.

A comparison of serum inflammatory cytokines according to phenotype in patients with psoriasis

Summary Background  Plaque‐type psoriasis manifests with various morphological phenotypes and different clinical activity over time in the same individual or from one patient to another. Circulating cytokines, especially T‐helper (Th) 1‐ and Th17‐related, have been suggested to reflect the inflammatory nature of psoriasis. However, studies regarding cytokine profile according to morphological phenotypes are quite scarce.

Clinical characteristics and risk of melanoma development from giant congenital melanocytic naevi in Korea: a nationwide retrospective study.

Background  Giant congenital melanocytic naevi (GCMN) are known risk factors for the development of melanoma. However, melanoma risk among Asians is rarely evaluated.

Molecular analysis of malassezia microflora on the skin of the patients with atopic dermatitis.

BACKGROUND The yeasts of the genus Malassezia are members of the normal flora on human skin and they are found in 75~80% of healthy adults. Since its association with various skin disorders have been known, there have been a growing number of reports that have implicated Malassezia yeast in atopic dermatitis (AD). OBJECTIVE The aim of the present study is to isolate the various Malassezia species from AD patients by using 26S rDNA (ribosomal Deoxyribonucleic acid) PCR-RFLP and to investigate the relationship between a positive Malassezia culture and the severity of AD. METHODS Cultures for Malassezia yeasts were taken from the scalp, cheek, chest, arm and thigh of 60 patients with atopic dermatitis. We used a rapid and accurate molecular biological method 26S rDNA PCR-RFLP, and this method can overcome the limits of the morphological and biochemical methods. RESULTS Positive Malassezia growth was noted on 51.7% of the patients with atopic dermatitis by 26S rDNA PCR-RFLP analysis. The overall dominant species was M. sympodialis (16.3%). M. restricta was the most common species on the scalp (30.0%) and cheek (16.7%). M. sympodialis (28.3%) was the most common species on the chest. The positive culture rate was the highest for the 11~20 age group (59.0%) and the scalp showed the highest rate at 66.7%. There was no significant relationship between the Malassezia species and SCORing for Atopic Dermatitis (SCORAD). CONCLUSION The fact that the cultured species was different for the atopic dermatitis lesion skin from that of the normal skin may be due to the disrupted skin barrier function and sensitization of the organism induced by scratching in the AD lesion-skin. But there was no relationship between the Malassezia type and the severity score. The severity score is thought to depend not on the type, but also on the quantity of the yeast.

Epidemiologic Study of Malassezia Yeasts in Seborrheic Dermatitis Patients by the Analysis of 26S rDNA PCR-RFLP

BACKGROUND This case-control study concerns a molecular biological method based on the data gathered from a group of Korean subjects to examine the distribution of Malassezia yeasts in seborrheic dermatitis (SD) patients. Cultures for Malassezia yeasts were taken from the foreheads, cheeks and chests of 60 patients with SD and in 60 healthy controls of equivalent age. OBJECTIVE The purpose of this study is to identify the relationship between certain species of Malassezia and SD. This was done by analyzing the differences in the distribution of Malassezia species in terms of age and body parts of the host with healthy controls. METHODS 26S rDNA PCR-RFLP, a fast and accurate molecular biological method, was used to overcome the limits of morphological and biochemical methods. RESULTS The positive Malassezia culture rate was 51.7% in patients with SD, which was lower than that of healthy adults (63.9%). M. restricta was dominant in patients with SD (19.5%). Likewise, M. restricta was identified as a common species (20.5%) in healthy controls. In the ages 31~40, M. restricta was found to be the most common species (31.6%) among SD patients. CONCLUSION According to the results of the study, the most frequently isolated species was M. restricta (19.5%) in patients with SD. There was no statistically significant difference in the distribution of Malassezia species between the SD patients and healthy control groups.