Molecular analysis of Malassezia microflora in seborrheic dermatitis patients: comparison with other diseases and healthy subjects

Malassezia species colonize the skin of normal and various pathological conditions including pityriasis versicolor (PV), seborrhoeic dermatitis (SD) and atopic dermatitis (AD). To elucidate the pathogenic role of Malassezia species in SD, Malassezia microflora of 31 Japanese SD patients was analyzed using a PCR-based, culture-independent method. Nested PCR assay using the primers in the rRNA gene indicated that the major Malassezia species in SD were M. globosa and M. restricta, found in 93 and 74% of the patients, respectively. The detection rate and number of each species varied similarly in SD, PV and healthy subjects (HSs), whereas AD showed higher values. Real-time PCR assay showed that the lesional skin harbored approximately three times the population of genus Malassezia found in nonlesional skin (P<0.05), and that M. restricta is a significantly more common species than M. globosa in SD (P<0.005). Genotypic analysis of the rRNA gene showed that the M. globosa and M. restricta from SD patients fell into specific clusters, and could be distinguished from those collected from HSs, but not from those colleted from AD patients. Our results indicate that certain strains of M. restricta occur in the lesional skin of SD patients.     

Functional analyses of the skin surface of the areola mammae: comparison between healthy adult male and female subjects and between healthy individuals and patients with atopic dermatitis

Background Although the nipple and areola of the breast constitute a unique and prominent area on the chest, so far no study has been done on the functional properties of their skin surfaces. Objective To study the stratum corneum (SC) covering the areola using noninvasive methods. Methods Eighteen adult healthy subjects comprising nine men and nine women and 18 age‐ and sex‐matched patients with atopic dermatitis (AD), none of whom had visible skin lesions, participated in the study. Transepidermal water loss (TEWL), skin surface hydration and skin surface lipid levels were measured on the areola and adjacent breast skin. The size of the skin surface corneocytes of these skin regions was assessed. Results All the healthy subjects showed significantly higher TEWL accompanied by smaller sized corneocytes on the areola than on the adjacent breast skin. Only female subjects revealed a significantly higher skin surface hydration state together with significantly increased skin surface lipid levels on the areola than on the adjacent breast skin. These sex differences were observed even in patients with AD. Comparison between healthy individuals and the patients with AD demonstrated higher TEWL, decreased skin surface hydration state and lower skin surface lipid levels associated with smaller sized corneocytes in the areola in the patients with AD, especially in male patients. Conclusions In adults, the SC barrier function and SC water‐binding capacity of the areola were functionally poorer than in the adjacent skin, being covered by smaller sized corneocytes and lower amounts of skin surface lipids, especially in men and in patients with AD.     

Knock‐down of filaggrin does not affect lipid organization and composition in stratum corneum of reconstructed human skin equivalents

Human skin mainly functions as an effective barrier against unwanted environmental influences. The barrier function strongly relies on the outermost layer of the skin, the stratum corneum (SC), which is composed of corneocytes embedded in an extracellular lipid matrix. The importance of a proper barrier function is shown in various skin disorders such as atopic dermatitis (AD), a complex human skin disorder strongly associated with filaggrin (FLG) null mutations, but their role in barrier function is yet unclear. To study the role of FLG in SC barrier properties in terms of SC lipid organization and lipid composition, we generated an N/TERT‐based 3D‐skin equivalent (NSE) after knock‐down of FLG with shRNA. In these NSEs, we examined epidermal morphogenesis by evaluating the expression of differentiation markers keratin 10, FLG, loricrin and the proliferation marker ki67. Furthermore, the SC was extensively analysed for lipid organization, lipid composition and SC permeability. Our results demonstrate that FLG knock‐down (FLG‐KD) did not affect epidermal morphogenesis, SC lipid organization, lipid composition and SC permeability for a lipophilic compound in NSEs. Therefore, our findings indicate that FLG‐KD alone does not necessarily affect the functionality of a proper barrier function.     

Skin surface lipids in HIV sero-positive and HIV sero-negative patients affected with seborrheic dermatitis.

Skin surface lipids of patients affected with seborrheic dermatitis both HIV sero-negative (C group) and HIV sero-positive (B group) have been studied by capillary Gas chromatography-Mass spectrometry (GC-MS) in comparison with normal age matched controls (A group) to determine whether, among the three groups of individuals, there were qualitative and quantitative changes in lipid class composition and in the fatty acid and alcohol components of lipid fractions. With regard to percent composition of skin surface lipid fractions, no significant differences were found between HIV sero-positive and HIV sero-negative patients with seborrheic dermatitis. The observed significant reduction of total lipids (micrograms/sq cm) in the sites affected with the disease in comparison with controls was associated with a slight but significant decrease of squalene (P less than 0.05) and with a corresponding increase of cholesterol and cholesterol esters (P less than 0.05). These abnormalities in lipid fractions and total lipids were not observed in the uninvolved skin of subjects with seborrheic dermatitis. Fatty acid and alcohol patterns of skin lipid fractions were not significantly different among the three groups of individuals.     

Evaluation of efficacy of a skin lipid mixture in patients with irritant contact dermatitis, allergic contact dermatitis or atopic dermatitis: a multicenter study

Disturbances of skin barrier function occur in several skin diseases, e.g., atopic dermatitis (AD), irritant/allergic contact dermatitis (ICD, ACD). Skin barrier damage triggers the production of cytokines that stimulate lipogenesis which may also cause inflammatory processes. The aim of this study was to evaluate the efficacy of a topical skin lipid mixture in the treatment of ICD, ACD and AD. 580 consecutive patients suffering from ICD, ACD or AD were treated with a skin lipid mixture containing ceramide-3 and patented nanoparticles. Patients received the lipid mixture alone or in combination with topical corticosteroids until clearance or for 8 weeks. Both treatment groups statistically improved all parameters considered at week 4 and 8 as compared to baseline. Between the 2 treatment groups, there was a statistically significant difference in favour of combined therapy for (ICD, ACD, AD, respectively): erythema, pruritus and overall disease severity; erythema and pruritus; erythema, pruritus, fissuring and overall disease severity. No statistically significant difference was found for (ICD, ACD, AD, respectively): dryness, scaling and fissuring; scaling, fissuring and overall disease severity; dryness and scaling. Between the 2 ACD treatment groups, there was a statistically significant difference in favour of the skin lipid mixture for dryness. In conclusion, the study shows that balanced lipid mixtures are effective in improving barrier properties and the clinical condition of the skin in contact dermatitis.     

The lack of a relationship between atopic dermatitis and nonmelanoma skin cancers

BACKGROUND: Very little has been published on whether a relationship exists between atopic dermatitis (AD) and skin cancer. OBJECTIVE: The goal of this study was to investigate whether individuals with AD are more likely than other patients with dermatologic conditions to develop nonmelanoma skin cancer. METHODS: This was a case-control, mailed-survey study. RESULTS: Of those contacted, 69.8% (3207 of 4591) filled out the survey. Of the control patients, 18.4% (254) had a history of AD as defined by the United Kingdom Working Party diagnosis criteria and composed 13.7% (210) of the cases. The unadjusted odds ratio of AD to nonmelanoma skin cancer was 0.70 (95% confidence interval 0.57-0.85). After fully adjusting for age, sex, ethnicity, and topical steroid use the odds ratio was 0.78 (0.61, 0.98). Using different definitions of AD had little effect on this result. CONCLUSIONS: It does not appear that patients with a history of AD are more likely to develop nonmelanoma skin cancers than other patients with dermatologic conditions.     

Multiple tissue kallikrein mRNA and protein expression in normal skin and skin diseases

BACKGROUND: Human tissue kallikreins are a gene family (KLK1-KLK15) encoding for 15 secretory serine proteases (hK1-hK15). Two tissue kallikrein proteins, hK5 and hK7, were previously found in the stratum corneum (SC), stratum granulosum (SG) and appendages. hK8 was also shown to be secreted via lamellar granules and numerous KLK mRNAs were previously identified. KLKs are believed to be responsible for desquamation of corneocytes and sebum, sweat and hair maturation. OBJECTIVES: To demonstrate immunohistochemically the expression of hK6, hK8 and hK13 in normal skin tissue and to show an increased cell number expressing kallikrein mRNAs and proteins in psoriasis vulgaris (PV) and atopic dermatitis (AD). METHODS: Samples of normal, PV and AD skin were obtained. hK6-, hK8- and hK13-specific antibodies were produced and used for immunohistochemical analysis. Multiple KLK mRNAs were synthesized and used for in situ hybridization study. RESULTS: Three other hKs, namely hK6, hK8 and hK13, were immunohistochemically identified as new skin serine proteases in the whole SC, SG, sebaceous glands, eccrine sweat glands, hair follicles and nerves. We also demonstrated an increased number of cells expressing KLK mRNAs and hKs in PV and AD. In PV, KLK mRNAs/hKs were predominantly expressed in the upper epidermis. In AD, hK distribution was rather diffuse and expanded into the lower epidermis. CONCLUSIONS: The colocalization of various hKs seems to be essential for the regulation of serine protease activity in skin and for steady desquamation and skin barrier function. Moreover, the increased number of cells expressing multiple KLK mRNA and hK in PV and AD could be a clue to elucidate their pathogenesis.     

Increased HMGB1 serum levels and altered HMGB1 expression in patients with psoriasis vulgaris

High mobility group box-1 (HMGB1) has been implicated as a pro-inflammatory cytokine in the pathogenesis of various inflammatory and autoimmune diseases. However, information about HMGB1 in inflammatory skin diseases is unknown. Herein, we investigated the serum HMGB1 levels and tissue HMGB1 expression in patients with psoriasis vulgaris (PV) and atopic dermatitis (AD). Serum levels of HMGB1 in patients with PV and AD were detected by enzyme-linked immunosorbent assay (ELISA). The expression of HMGB1 in lesional skin was evaluated by immunohistochemistry and immunofluorescence. Protein levels of HMGB1 in the nuclear fraction and cytoplasmic fraction were determined by western blot. Serum levels of HMGB1 in patients with PV but not AD were significantly higher than those in nornal controls. Moreover, serum HMGB1 levels were correlated with the severity of PV according to PASI socres. Furthermore, by immunohistochemistry and immunofluorescence, we showed that the expression of HMGB1 in normal skin was almost completely restricted to the nucleus. However, abundant cytoplasmic expression of HMGB1 was observed in the epidermis in lesional skin of PV patients. In addition, western blot data indicated that HMGB1 expression was in the nucleus protein and was absent in the cytoplasm protein in control group. In contrast, HMGB1 expression in the cytoplasmic fraction was detectable in AD patients and more distinct in PV patients. Taken together, this study provides first observations on the association of HMGB1 with PV, and showed the elevated HMGB1 serum levels and altered HMGB1 distribution in lesional skin in patients with PV. We suggest that HMGB1 might be involved in the pathogenesis of PV.     

Deficiency of n‐6 polyunsaturated fatty acids is mainly responsible for atopic dermatitis‐like pruritic skin inflammation in special diet‐fed hairless mice

Hairless mice fed a special diet, HR‐AD, develop atopic dermatitis (AD)‐like skin inflammation with skin barrier defects and itch‐related scratching; however, the ingredient(s) causing the dermatitis remains unclear. In this study, we examined whether deficiency of certain polyunsaturated fatty acids (PUFAs) is involved in HR‐AD‐induced AD. High‐purity PUFAs were given to HR‐AD‐fed mice by dietary supplementation or gavage. Fatty acid levels in the serum and skin were determined by using gas chromatography–mass spectrometry. In serum from HR‐AD‐fed mice, linoleic acid (LA, 18:2n‐6) and α‐linolenic acid (ALA, 18:3n‐3), as well as their metabolites, were markedly decreased. When mice were fed HR‐AD supplemented with LA or ALA in an amount equal to that contained in a normal diet, the development of AD‐like symptoms was completely prevented by supplementation with LA but not with ALA. Relatively high dose of ALA slightly alleviated skin barrier defects, but did neither itch‐related scratching nor skin inflammation. On the other hand, gavage administration of LA metabolites, such as γ‐linolenic acid and arachidonic acid (AA), significantly ameliorated established dermatitis without increasing LA in the serum and skin. Moreover, AA‐induced amelioration of dermatitis was not affected by pharmacological blockade of 5‐lipoxygenase (5‐LOX) and cyclooxygenase (COX), suggesting no involvement of 5‐LOX‐ or COX‐mediated AA metabolites in the amelioration. In conclusion, our results indicate that deficiency of n‐6 PUFAs is mainly responsible for AD‐like symptoms by HR‐AD feeding. Thus, this model could be useful for studying the pathomechanisms associated with deficiency of n‐6 PUFAs in AD.     

Water, salts and skin barrier of normal skin

Background: We recently reported that open application of seawater for 20 min ameliorated experimental irritant contact dermatitis induced by sodium lauryl sulphate (SLS) cumulative irritation. The efficacy was overall contributed by 500 mm of sodium chloride (NaCI) and 10 mm of potassium chloride (KCl), which are consistent with the each concentration in seawater. Although the usefulness of mineral water with 500 mm NaCl and 10 mm KCl to treat atopic dermatitis (AD) or irritated skin was considered, seawater or its components would induce a feel of stinging in patients with AD. Furthermore, 20 min application was thought to be too long to use everyday as a treatment. Objective: We report the effects of 3 types of mineral water with NaCl and KCl to check the further efficacy with lesser stinging by 2 min application. Results: A mineral water with 250 mm NaCl and 50 mm KCl was the most effective water to prevent disruption of skin barrier and stratum corneum water content after cumulating irritation by SLS. Moreover, improvement of skin dryness and pruritus were shown 2 weeks after the application of the mineral water to a 6‐year‐old boy with atopic dermatitis. Conclusion: Our results suggested the possible usefulness of the mineral water with 250 mm NaCl and 50 mm KCl as the therapy of atopic dermatitis of other chronic dermatitis. Although the mineral water would not cure those skin diseases, it could be an adjunctive therapy. Further controlled clinical trials with evaluation by TEWL and capacitance are required to declare the efficacy of the mineral water in the treatment of patients with AD or other chronic dermatitis.     

Deficient production of hexadecenoic acid in the skin is associated in part with the vulnerability of atopic dermatitis patients to colonization by Staphylococcus aureus

BACKGROUND AND OBJECTIVES: As one of the major skin fatty acids, cis-6-hexadecenoic acid (C16:1Delta6) exhibits a specific antibacterial activity and might play a specific role in the defense mechanism against Staphylococcus aureus, in healthy subjects whereas S. aureus frequently colonizes the skin of patients with atopic dermatitis (AD). METHODS: Fatty acid composition of sebum at the recovery level was analyzed by gas chromatography and S. aureus colonizing the skin was assessed by the 'cup-scrub' method (9 patients and 10 healthy controls). To evaluate in vivo effect of C16:1Delta6 on colonization, C16:1Delta6 was applied for 2 weeks on the upper arm skin of another group of AD patients (11 patients). RESULTS: Analysis of sebum lipids revealed that there is a significant lower free C16:1Delta6 content in nonlesional skin from AD patients compared with healthy controls. This lower content is also accompanied by a significantly lower level of C16:1Delta6 in the total fatty acid composition of sebum (analyzed following hydrolysis). The lower level of free C16:1Delta6 correlated significantly (R(2) = 0.41, p < 0.01) with the numbers of S. aureus colonizing nonlesional skin. Topical application of free C16:1Delta6 on the skin of AD patients for 2 weeks abolished the markedly increased bacterial count in 6 out of the 8 AD patients tested. CONCLUSIONS: Free C16:1Delta6 may be involved in the defense mechanism against S. aureus in healthy skin and this deficit triggers the susceptibility of the skin to colonization by S. aureus in AD.     

Increased level of high mobility group box 1 in the serum and skin in patients with generalized pustular psoriasis

High-mobility group box 1 (HMGB-1) is a highly abundant pro-inflammatory protein associated with the pathogenesis of inflammatory and autoimmune diseases. HMGB-1 expression level increases in patients with psoriasis vulgaris (PV). However, HMGB-1 expression in patients with generalized pustular psoriasis (GPP) is unknown. In this study, we investigated HMGB-1 expression in GPP. HMGB-1 expression levels were examined in the skin and serum of patients with GPP, PV, atopic dermatitis (AD) and healthy controls (HC) using enzyme-linked immunosorbent assay and immunohistochemistry. The elevation in HMGB-1 expression was significantly higher in GPP patients than in PV, AD and HC patients. In addition, patients with GPP had elevated serum HMGB-1 levels compared with those with AD and HC. Furthermore, serum HMGB-1 levels were significantly decreased after systemic treatment. In the correlation analysis, a significant positive correlation was detected between serum HMGB-1 levels and the Japanese severity score for GPP. HMGB-1 may be involved in the pathogenesis of GPP and can be useful to evaluate disease severity and the effectiveness of GPP treatment.     

Comparison of skin barrier function and sensory nerve electric current perception threshold between IgE-high extrinsic and IgE-normal intrinsic types of atopic dermatitis

Background  Two types of atopic dermatitis (AD) have been proposed, with different pathophysiological mechanisms underlying this seemingly heterogeneous disorder. The extrinsic type shows high IgE levels presumably as a consequence of skin barrier damage and feasible allergen permeation, whereas the intrinsic type exhibits normal IgE levels and is not mediated by allergen-specific IgE.
Objectives  To investigate the relationship between pruritus perception threshold and skin barrier function of patients with AD in a comparison between the extrinsic and intrinsic types.
Methods  Enrolled in this study were 32 patients with extrinsic AD, 17 with intrinsic AD and 24 healthy individuals. The barrier function of the stratum corneum was assessed by skin surface hydration and transepidermal water loss (TEWL), and pruritus perception was evaluated by the electric current perception threshold (CPT) of sensory nerves upon neuroselective transcutaneous electric stimulation.
Results  Skin surface hydration was significantly lower and TEWL was significantly higher in extrinsic AD than intrinsic AD or normal controls. Although there was no statistically significant difference in CPT among extrinsic AD, intrinsic AD and normal controls, CPT was significantly correlated with skin surface hydration and inversely with TEWL in intrinsic AD and normal controls, but not extrinsic AD. Finally, CPT was correlated with the visual analogue scale of itch in the nonlesional skin of patients with extrinsic but not intrinsic AD.
Conclusions  Patients with extrinsic AD have an impaired barrier, which increases the pre-existing pruritus but rather decreases sensitivity to external stimuli. In contrast, patients with intrinsic AD retain a normal barrier function and sensory reactivity to external pruritic stimuli.     

对遗传过敏性皮炎的乙酸胆硷、组胺皮试和皮肤划痕反应的评价

在不同性质的炎症性皮肤病以乙酰胆碱、组胺皮试和皮肤划痕试验,提示在遗传过敏性皮炎(AD)的皮损和外表正常皮肤处的异常反应表现突出,虽非特异,但对诊断有参考价值.皮试的异常反应,除继发于炎症性改变外,通过对不同AD亚型和在不同部位试验的分析比较,发现与遗传过敏性素质有关.     

SKIN SURFACE LIPIDS IN HIV-POSITIVE PATIENTS WITH AND WITHOUT SEBORRHEIC DERMATITIS

Background. Seborrheic dernnatitis (SD) is a frequent complication of infection with the human immunodeficiency virus (HIV). Most studies examining the cause of SD have concentrated on the roles of Pityrosporum ovale and sebaceous lipids. Previous studies of skin surface lipid from patients with SD have produced conflicting results, with some authors reporting an abnormal lipid composition and others finding little or no abnormality. Methods. The composition of skin surface lipid was studied in 15 HIV-positive and 10 HIV-negative men with SD, in 14 HIV-positive men without SD, and in 16 unaffected controls. Total lipids were extracted from unaffected forehead skin into petroleum ether and separated into lipid classes by thin layer chromatography. The lipid classes were quantitated by densitometry after charring with sulfuric acid. Results. Patients, HIV-positive with SD, had significantly lower proportions of free fatty acid (FFA) and higher levels of triglyceride than normal controls. Patients, HIV-positive without SD, had a significantly increased proportion of FFA compared to HIV-positive patients with SD. Patients with SD, both HIV-positive and HIV-negative, had a similar pattern of skin surface lipid. Levels of FFA were lower and those of triglyceride higher than in the patients unaffected by SD, whether HIV-positive or not. There was no significant difference found between groups in free cholesterol, wax esters, and squalene. Conclusions. Abnormalities of skin surface lipid composition may play a part in the development of SD in both HIV-positive and HIV-negative men.     

Skin absorption through atopic dermatitis skin: a systematic review

Patients with atopic dermatitis (AD) have skin barrier impairment in both lesional and nonlesional skin. They are typically exposed daily to emollients and intermittently to topical anti‐inflammatory medicaments, thereby increasing the risk of developing contact allergy and systemic exposure to chemical ingredients found in these topical preparations. We systematically searched for studies that investigated skin absorption of various penetrants, including medicaments, in patients with AD, but also in animals with experimentally‐induced dermatitis. We identified 40 articles: 11 human studies examining model penetrants, 26 human studies examining AD drugs, and three animal studies. We conclude that patients with AD have almost twofold increased skin absorption compared with healthy controls. There is a need for well‐designed epidemiological and dermatopharmacokinetic studies that examine to what extent AD causes patients to be systemically exposed to chemicals compared with nonatopic dermatitis.     

Characteristics of skin surface morphology and transepidermal water loss in clinically normal-appearing skin of patients with atopic dermatitis: a video-microscopy study

In patients with atopic dermatitis (AD), it is debatable whether clinically normal-appearing skin is equal to non-atopic normal skin. The aim of this study was to quantitatively evaluate the characteristics of normal-appearing skin of AD. We examined the value of skin surface morphological changes using a new, simple, computer-assisted method with a video microscope. We also investigated the physiological function as represented by transepidermal water loss (TEWL) levels in 44 patients with AD and 15 normal controls. The morphological changes were represented by a variation coefficient score that reflected the irregularity of skin ridges, named the surface irregularity index (SII). There were significant differences between the normal-appearing skin of AD and non-atopic normal skin in both SII (P<0.001) and in TEWL (P<0.01). Especially for the SII, there were significant differences between AD subgroups subdivided by peripheral blood eosinophil count (Eo), serum lactate dehydrogenase level, and clinical score. TEWL values were significantly higher in the high-Eo AD group (n=15) than in the low-Eo AD group (n=29) (P<0.05). These findings indicate that clinically normal-appearing skin of AD patients with high disease activity differs from non-atopic normal skin in both surface morphology and physiology and that these changes reflect the current disease activity.     

蛋白酶激活受体2在特应性皮炎患者皮损组织中的表达与分布研究

目的:观察蛋白酶激活受体(PAR)2及其相关蛋白在特应性皮炎(AD)患者皮损组织中的表达,探索AD的发病机制.方法:AD患者15例,正常对照10例,应用免疫组化方法(ABC法),对皮肤组织中PAR2的表达及组织分布进行测定.结果:AD患者皮损组织呈现以慢性皮炎为主的病理改变:表皮突向下增生延长,棘层肥厚,细胞增生明显;真皮浅层血管周围淋巴单一核细胞浸润,患者非皮损组织未见明显的炎性细胞浸润,但可见轻度棘层细胞增生.PAR2表达水平在AD患者皮损组织中明显升高,但在AD患者非皮损组织中变化并不显著.结论:在AD患者中,PAR2表达水平异常增加,由于PAR2表达的增加主要见于AD患者的皮损组织,南此推测.PAR2的激活和表达主要与AD的早期急性炎症反应有直接关联.     

Increased carbonyl protein level in the stratum corneum of inflammatory skin disorders: A non‐invasive approach

The stratum corneum (SC) is the interface of body and environment, and is continuously exposed to oxidative stress, resulting in carbonyl modification of proteins. We have developed a simple and non‐invasive method to assess carbonyl protein (CP) level in the SC, applied it to various kinds of skin, and revealed a link between the stratum corneum carbonylated protein (SCCP) level and water content in the SC. The purpose of the present study is to examine the SCCP level in inflammatory skin disorders associated with xerosis. Psoriasis vulgaris (PV) and atopic dermatitis (AD) are typical inflammatory skin disorders, of which the stratum corneum shows markedly low water content. SC samples were non‐invasively collected from the lesional and non‐lesional areas of PV and AD by adhesive tape stripping, and their carbonyl groups were determined by reaction with fluorescein‐5‐thiosemicarbazide. The average fluorescence intensity of the SC was calculated as SCCP level. Higher SCCP level was observed in the lesional area of PV as compared with non‐lesional area or healthy control. Lesional area of AD also exhibited higher SCCP level than corresponding non‐lesional area, of which SCCP level was slightly higher than the healthy control. These data suggest the involvement of oxidative modification of the SC protein, at least in part, in generation of xerotic skin in inflammatory skin disorders as well as dry skin in healthy subjects.     

Stratum corneum lipid abnormalities in atopic dermatitis

Summary Patients with atopic dermatitis (AD) often present with a dry skin. To clarify the relationship between dry skin and lipid abnormalities within stratum corneum, stratum corneum lipids were collected from six AD patients aged 15 to 25 years and from sex- and age-matched controls. All major stratum corneum lipid classes were separated and quantitated by high-performance thin-layer chromatography/photodensitometry. Six ceramide fractions were also isolated and quantitated by thin-layer chromatography/photodensitometry. Esterified fatty acids of both ceramide 1 (acylceramides) and wax esters were analysed by capillary gas chromatography. The relative amounts of all the stratum corneum lipid classes including squalene, cholesterol esters, wax esters, triglycerides, free fatty acids, cholesterol, ceramides, cholesterol sulphate and phospholipids did not differ statistically between AD patients and controls. However, a significant decrease in proportion of ceramide 1, which is believed to be a carrier of linoleate responsible for a water-barrier function, and increased levels of esterified C₁₈₁ fatty acids (oleate) of ceramide 1 were observed in AD patients. On the other hand, the fatty acid compositions as well as the proportions of C₁₆₁ straight-chain component in sebum wax esters of AD patients were very similar to those of controls. These results suggest that a significantly reduced amount and/or structural alterations of ceramide 1 deriving from epidermal keratinocytes may be responsible for the impaired water-barrier function of the skin in AD.