Malassezia-Hefen und ihre Bedeutung in der Dermatologie

Yeasts of the genus Malassezia belong to the normal microflora of the human skin. In addition they are known to cause a variety of skin diseases; the most frequent of which is pityriasis versicolor. Malassezia yeasts are also thought to be associated with seborrheic dermatitis, dandruff and Malassezia folliculitis. Recently the significance of Malassezia yeasts as a trigger factor for atopic dermatitis of the head and neck region has been pointed out. The role of the Malassezia yeasts in these different diseases has been controversial in the past and remains an issue because of difficulties in isolation, culture and differentiation of the organism. Thanks to molecular techniques, 10 species can actually be differentiated. The article presents the different Malassezia-associated diseases, their clinical picture, diagnosis and appropriate therapy. In addition the speciation of Malassezia is reviewed.     

Skin diseases associated with Malassezia species

The yeasts of the genus Malassezia have been associated with a number of diseases affecting the human skin, such as pityriasis versicolor, Malassezia (Pityrosporum) folliculitis, seborrheic dermatitis and dandruff, atopic dermatitis, psoriasis, and--less commonly--with other dermatologic disorders such as confluent and reticulated papillomatosis, onychomycosis, and transient acantholytic dermatosis. Although Malassezia yeasts are a part of the normal microflora, under certain conditions they can cause superficial skin infection. The study of the clinical role of Malassezia species has been surrounded by controversy because of their fastidious nature in vitro, and relative difficulty in isolation, cultivation, and identification. Many studies have been published in the past few years after the taxonomic revision carried out in 1996 in which 7 species were recognized. Two new species have been recently described, one of which has been isolated from patients with atopic dermatitis. This review focuses on the clinical, mycologic, and immunologic aspects of the various skin diseases associated with Malassezia. It also highlights the importance of individual Malassezia species in the different dermatologic disorders related to these yeasts.     

Seborrheic dermatitis

Seborrheic dermatitis is a common inflammation of the skin, occurring most often on the face, scalp and chest. It is closely related to infantile seborrheic dermatitis, or diaper rash. Seborrheic dermatitis is particularly common in patients with Parkinson's disease or with HIV/AIDS. The recent resurgence of interest in Malassezia yeasts has revived the old hypothesis that seborrheic dermatitis is caused by an altered relationship between these skin commensals and the host. Moreover, the success of antifungal medications in treating seborrheic dermatitis provides new evidence for this view. LEARNING OBJECTIVE: Upon completing this paper, the reader should be aware of the clinical presentation of seborrheic dermatitis and which populations are at particular risk of developing this disorder. In addition, s/he will be aware of the role of Malassezia yeasts in seborrheic dermatitis and the way in which knowledge of the importance of these yeasts has altered the treatment of this disorder.     

The effects of Malassezia yeasts on cytokine production by human keratinocytes

Yeasts of Malassezia, members of the microbiologic flora of the skin, cause pityriasis versicolor and have also been implicated in the pathogenesis of other superficial dermatoses; the most important ones are seborrheic dermatitis, folliculitis, and atopic dermatitis. The mechanisms by which the yeasts cause these dermatose? however, are not yet clear, and there have been no studies on the interaction between fungi and keratinocytes, especially the effects of fungi on the production of cytokines by human keratinocytes. Recently, the genus Malassezia has been expanded to seven species based on molecular data. In this study, we estimated the effects of Malassezia yeasts on cytokine (interleukins 1beta, 6, and 8, monocyte chemotactic protein-1, and tumor necrosis factor-alpha) production by human keratinocytes in order to examine whether the pathogenicity of the respective Malassezia yeasts is different from each other and to elucidate the mechanism by which Malassezia yeasts cause the dermatoses with different clinical and pathologic manifestations. Variable levels of interleukin 6 and 8, and tumor necrosis factor-alpha in the supernatants in response to Malassezia yeasts (except M. furfur) increased from 1 to 24 h co-culture, but the monocyte chemotactic protein-1 was undetectable. Furthermore, cytokine levels in the supernatants were undetectable 1-24 h after the keratinocytes were harvested with only supernatants of Malassezia. These results indicate that Malassezia stimulates cytokine production by keratinocytes, the cytokine production needs the presence of Malassezia, and there are differences in ability to induce cytokine production by human keratinocytes among Malassezia yeasts. These differences may reflect the different inflammatory responses in Malassezia-associated dermatoses, resulting in different clinical and pathologic manifestations.     

Ciclopirox 1% shampoo for the treatment of seborrheic dermatitis

Seborrheic dermatitis is a chronic superficial fungal infection of the skin, particularly affecting sites rich in sebaceous glands. Although the precise etiology of seborrheic dermatitis is uncertain, yeasts of the genus Malassezia are known to play a causative role. Ciclopirox is a broad-spectrum, hydroxypyridone-derived, synthetic antifungal agent, which also has anti-inflammatory properties. Ciclopirox is effective both in vitro and in vivo against Malassezia yeasts, making it a valuable option for the treatment of seborrheic dermatitis. Varying frequencies and concentrations of ciclopirox shampoo have been shown to be effective and safe in the treatment of seborrheic dermatitis of the scalp.     

Malassezia species in healthy skin and in dermatological conditions

The genus Malassezia comprises lipophilic species, the natural habitat of which is the skin of humans and other warm‐blooded animals. However, these species have been associated with a diversity of dermatological disorders and even systemic infections. Pityriasis versicolor is the only cutaneous disease etiologically connected to Malassezia yeasts. In the other dermatoses, such as Malassezia folliculitis, seborrheic dermatitis, atopic dermatitis, and psoriasis, these yeasts have been suggested to play pathogenic roles either as direct agents of infection or as trigger factors because there is no evidence that the organisms invade the skin. Malassezia yeasts have been classified into at least 14 species, of which eight have been isolated from human skin, including Malassezia furfur, Malassezia pachydermatis, Malassezia sympodialis, Malassezia slooffiae, Malassezia globosa, Malassezia obtusa, Malassezia restricta, Malassezia dermatis, Malassezia japonica, and Malassezia yamatoensis. Distributions of Malassezia species in the healthy body and in skin diseases have been investigated using culture‐based and molecular techniques, and variable results have been reported from different geographical regions. This article reviews and discusses the latest available data on the pathogenicity of Malassezia spp., their distributions in dermatological conditions and in healthy skin, discrepancies in the two methods of identification, and the susceptibility of Malassezia spp. to antifungals.     

Role of Antifungal Agents in the Treatment of Seborrheic Dermatitis

Seborrheic dermatitis is a superficial fungal disease of the skin, occurring in areas rich in sebaceous glands. It is thought that an association exists between Malassezia yeasts and seborrheic dermatitis. This may, in part, be due to an abnormal or inflammatory immune response to these yeasts. The azoles represent the largest class of antifungals used in the treatment of this disease to date. In addition to their antifungal properties, some azoles, including bifonazole, itraconazole, and ketoconazole, have demonstrated anti-inflammatory activity, which may be beneficial in alleviating symptoms. Other topical antifungal agents, such as the allylamines (terbinafine), benzylamines (butenafine), hydroxypyridones (ciclopirox), and immunomodulators (pimecrolimus and tacrolimus), have also been effective. In addition, recent studies have revealed that tea tree oil (Melaleuca oil), honey, and cinnamic acid have antifungal activity against Malassezia species, which may be of benefit in the treatment of seborrheic dermatitis. In cases where seborrheic dermatitis is widespread, the use of an oral therapy, such as ketoconazole, itraconazole, and terbinafine, may be preferred. Essentially, antifungal therapy reduces the number of yeasts on the skin, leading to an improvement in seborrheic dermatitis. With a wide availability of preparations, including creams, shampoos, and oral formulations, antifungal agents are safe and effective in the treatment of seborrheic dermatitis.     

Seborrheic dermatitis

Seborrheic dermatitis is present in 1% to 3% of immunocompetent adults, and is more prevalent in men than in women. Seborrheic dermatitis may be seen in conjunction with other skin diseases, such as rosacea, blepharitis or ocular rosacea, and acne vulgaris. Malassezia yeasts have been associated with seborrheic dermatitis. Abnormal or inflammatory immune system reactions to these yeasts may be related to development of seborrheic dermatitis. Treatment modalities for seborrheic dermatitis include keratolytic agents, corticosteroids, and more recently, antifungal agents. Antifungal agents do not carry a risk of skin atrophy or telangiectasia with prolonged use, and it is more prudent to consider antifungals than corticosteroid preparations. The wide range of antifungal formulations available (creams, shampoos, or oral) provides safe, effective, and flexible treatment options for seborrheic dermatitis.     

Malassezia yeasts in the pathogenesis of atopic dermatitis

Atopic dermatitis is a common skin condition, the aetiology of which is multifactorial, involving genetic, immunological and environmental factors. In recent years, it has been suggested that various microbial organisms may also be involved in the pathogenesis of the disease. Yeasts belonging to the Malassezia genus have received particular attention. These yeasts, known to be a part of the normal skin flora, have been shown to be capable of inducing immunoglobulin (Ig)E-mediated and T-cell mediated immune responses postulated to contribute to chronic inflammation in the skin, particularly in the head and neck region, where colonization with Malassezia is the greatest. Considerable evidence now exists to support this idea, raising the possibility that specific antifungal therapy may be a useful treatment measure in some atopic patients who have a head and neck pattern of dermatitis.     

Ciclopirox shampoo for treating seborrheic dermatitis

Seborrheic dermatitis is a common inflammatory skin disease, affecting between 1% and 3% of immunocompetent adults. While its cause is unknown, a number of predisposing factors have been reported, including the implications of Malassezia yeasts. Various treatment options are available, such as ciclopirox shampoo, which combines anti-Malassezia activity with an anti-inflammatory action. This agent has been shown to be an effective and safe treatment for seborrheic dermatitis of the scalp.     

HIV disease and Malassezia yeasts: a quantitative study of patients presenting with seborrhoeic dermatitis

Summary Seborrhoeic dermatitis (SD) is a disease that affects 1—3% of the general population, 3–5% of young adults and 20–83% of patients with AIDS. Malassezia yeasts have been associated with the pathogenesis of this condition. The association between the Malassezia yeasts and HIV-related SD is still a controversial subject. The objective of our study was to investigate the role of Malassezia yeasts in the pathogenesis of SD in the HIV population comparing the number of yeasts'cells with the severity of the disease and degree of immunosuppression. We used two quantitative counting methods: direct counting with Sellolape-stripped skin and recovery of the yeasts in culture using contact plates. This investigation has demonstrated that there is a trend between numbers of yeasts present on lesional skin, severity of SD and CD-4-positive T lymphocytes count in HIV-positive patients. No quantitative differences were observed between HTV-reiated and non-HIV related SD.     

The prevalence of Malassezia yeasts in patients with atopic dermatitis, seborrhoeic dermatitis and healthy controls

Cultures for Malassezia yeasts were taken from both normal-looking skin and lesional skin in 124 patients with atopic dermatitis, 16 patients with seborrhoeic dermatitis and from normal skin of 31 healthy controls. Positive Malassezia growth was found in fewer patients with atopic dermatitis (56%) than in patients with seborrhoeic dermatitis (88%) or in healthy controls (84%, p<0.01). In the patients with atopic dermatitis, fewer positive cultures were found in lesional (28%) than in non-lesional skin (44%, p<0.05), while positive cultures were found in 75% of both lesional and non-lesional skin of patients with seborrhoeic dermatitis (not significant). M. sympodialis dominated in patients with atopic dermatitis (46%) and in healthy controls (69%). In patients with seborrhoeic dermatitis both M. sympodialis and M. obtusa were cultured in 43%. A Malassezia species extract mixture would increase the possibility of detecting IgE sensitization to Malassezia in patients with atopic dermatitis.     

Optimal Management of Fungal Infections of the Skin, Hair, and Nails

Superficial fungal infections are chronic and recurring conditions. Tinea capitis is a scalp infection, primarily affecting prepubescent children. Ringworm infections, such as tinea corporis and tinea cruris, involve the glabrous skin. Tinea nigra is a rare mycotic infection that may be related to travel abroad. Piedra, black or white, is limited to the hair shaft without involvement of the adjacent skin. Pityriasis (tinea) versicolor and seborrheic dermatitis are dermatoses associated with yeasts of the genus Malassezia that affect the lipid-rich areas of the body. The taxonomy of the Malassezia yeasts has been revised to include nine species, eight of which have been recovered from humans. Tinea pedis, an infection of the feet and toes, is one of the most common forms of dermatophytosis. Onychomycosis is a fungal infection affecting the nail bed and nail plate; it may be chronic and can be difficult to treat. In instances where the superficial fungal infection is severe or chronic, an oral antifungal agent should be considered. Terbinafine, itraconazole, and fluconazole are oral antifungals that are effective in the treatment of superficial mycoses.     

Seborrheic dermatitis: an update

Seborrheic dermatitis is a chronic relapsing inflammatory skin disorder clinically characterized by scaling and poorly defined erythematous patches. The prevalence of adult seborrheic dermatitis is estimated at 5%. Although the exact cause of seborrheic dermatitis has yet to be understood, Malassezia yeasts, hormones (androgens), sebum levels and immune response are known to play important roles in its development. Additional factors including drugs, winter temperatures and stress may exacerbate seborrheic dermatitis. A variety of treatment modalities are available, including antifungal agents, topical low-potency steroids and calcineurin inhibitors (immunomodulators). This review summarizes current knowledge on the etiopathogenesis and therapy of adult seborrheic dermatitis.     

马拉色菌外分泌物的研究进展

马拉色菌为人体皮肤常住菌,亦是条件致病菌.马拉色菌与花斑糠疹、马拉色菌毛囊炎、特应性皮炎、头皮屑、脂溢性皮炎及银屑病等多种皮肤病相关.马拉色菌在生长繁殖过程中会产生多种外分泌物,包括蛋白质及代谢产物等.近年研究多集中在马拉色菌外分泌蛋白中,其中脂肪酶、蛋白酶、磷脂酶、脂氧合酶、过氧化氢酶和酸性磷酸酶等酶类物质的种类、数量、活性可能与马拉色菌的致病相关.马拉色菌外分泌性代谢产物研究较少,malassezin、吲哚[3,2?b]咔唑、β咔啉生物碱等代谢产物与生物体的功能变化有直接的联系.马拉色菌外分泌物的研究,对阐明马拉色菌的致病机制具有指导意义,可能为治疗提供新思路.     

马拉色菌属的研究进展

马拉色菌是一种寄生于人和动物正常皮肤表面的真菌,可导致机会感染而引起各种马拉色菌属相关疾病。马拉色菌的致病机制主要是分解脂质,导致角质形成细胞形态学改变和细胞凋亡。马拉色菌可引起花斑癣、脂溢性皮炎、马拉色菌毛囊炎等,在特应性皮炎中也起到变应原的作用。对于这些疾病的治疗可使用抗真菌药物。     

头皮屑和头皮脂溢性皮炎患者头皮脂类水平及马拉色菌数量的检测

目的:测定有头皮屑及头皮脂溢性皮炎患者与正常受试者头皮表面脂类水平及马拉色菌数量的差异。方法:使用sebumeter于洗发后连续4天测量受试者额、顶、枕部头皮皮脂,并于第4天真菌镜检马拉色菌,记录马拉色菌数量。结果:有头皮屑及头皮脂溢性皮炎组与正常对照组相比,马拉色菌数量显著增高,具有统计学意义(P<0.05)。头皮脂溢性皮炎组较头皮屑组的马拉色菌数量显著增高,具有统计学意义(P<0.05)。在头皮屑及头皮脂溢性皮炎组中,随着炎症程度加重,检出的马拉色菌孢子数增多。结论:马拉色菌感染可能与头皮屑多和脂溢性皮炎有关。     

The role of Malassezia in atopic dermatitis affecting the head and neck of adults

Atopic dermatitis is a common chronic skin condition. A subset of patients with head and neck dermatitis may have a reaction to Malassezia flora fueling their disease. Although there are no documented differences in Malassezia species colonization, patients with head and neck atopic dermatitis are more likely to have positive skin prick test results and Malassezia-specific IgE compared with healthy control subjects and patients with atopy without head and neck dermatitis. There is no clear relationship with atopy patch testing. The reaction to Malassezia is likely related to both humoral- and cell-mediated immunity. Clinically, Malassezia allergy may be suspected in patients with atopic dermatitis and: (1) head and neck lesions; (2) exacerbations during adolescence or young adulthood; (3) severe lesions recalcitrant to conventional therapy; and (4) other atopic diseases. There is literature to suggest that these patients will benefit from a 1- to 2-month course of daily itraconazole or ketoconazole followed by long-term weekly treatment.     

马拉色菌相关婴儿皮肤病

马拉色菌是人皮肤表面的常驻真菌，能引起婴儿花斑癣，并与婴儿脂溢性皮炎、婴儿特应性皮炎、新生儿头部脓疱病、婴儿及新生儿痤疮的发病相关。这种相关性主要表现在皮损处能检出马拉色菌，且抗真菌治疗有效，在婴儿特应性皮炎的发病中，主要作为抗原。由于婴儿和新生儿的皮肤屏障功能、机体免疫功能等尚不成熟，在患该类疾病时临床表现不典型，较成人有差异，治疗以外用药物为主。