Atopic Eczema/Dermatitis Syndrome and <i>Malassezia</i>

Abstract

Atopic dermatitis is a chronic multifactorial inflammatory skin disease, which has had a marked increase in prevalence during the last decades. Recently, a new nomenclature was recommended where the term ‘atopic eczema/dermatitis syndrome’ (AEDS) should be used to reflect the heterogeneity in this group of patients and where those patients without measurable IgE reactivity should be classified as either ‘nonallergic AEDS’ or ‘non-IgE-associated allergic AEDS’. For nearly 20 years it has been discussed whether the opportunistic yeast Malassezia, previously designated Pityrosporum, is a contributing factor to AEDS. Today there are several reports that demonstrate specific serum IgE or positive skin prick test and/or atopy patch test reactions to Malassezia in patients with AEDS. Several IgE-binding components have been identified in extracts of Malassezia ranging in molecular mass between 10 and 100 kD. The genes for nine Malassezia allergens with molecular weights ranging from 14 to 36 kD have hitherto been identified and cloned. Six of them are now produced by recombinant techniques and used in diagnostic tests. At present the genus Malassezia is subdivided into seven different species, which all have been isolated from human skin. The respective contribution of different Malassezia spp. to AEDS and in what proportion they share allergens remains to be clarified. We summarize here data that Malassezia can play a role in eliciting and maintaining eczema in patients with AEDS.

Cutaneous yeast microflora in patients with atopic dermatitis

“…There can also be a relationship between the AD-affected body part and the prevalent yeast genera: if Malassezia mostly colonize lipid-rich areas; Candida usually appear on hands and legs. The data obtained in the present study are similar to those from previous studies [10,14,40]. In the child group, the yeast colonization rate was significantly lower than in the adult group.…”

“…Sensitization to the yeast can be detected in approximately 50% of adult patients [10][11][12][13]. However, if majority of healthy individuals have IgG antibodies to Malassezia, 30%-80% of AD patients show IgE and/or T cell reactivity to the organism, demonstrating that Malassezia can act as an exacerbating factor [14]. The number of Malassezia yeast on AD skin is not always elevated; nevertheless, it may induce immunological changes, in which case reduction of yeast cells may result in AD improvement [15,16].…”

IgE‐reactivity to seven Malassezia species

“…Malassezia species (spp.) are considered to cause skin infections such as pityriasis versicolor and pityrosporum folliculitis (4-7) and they play an important role in the pathogenesis of seborrhoeic dermatitis and Ôatopic dermatitisÕ (8-12 and reviewed in 13).…”

“…42132, American Type Culture Collection (ATCC) was classified by biochemical characterization as M. sympodialis (17, J. Faergemann, personal communication). This strain has been used in several studies (13) and is the allergen source for the production of the m70 ImmunoCAP by Pharmacia, Diagnostic AB (Uppsala, Sweden) for measuring IgE antibodies specific for Malassezia in serum. Extract obtained from M. sympodialis induces higher T-cell responses in AEDS patients than in healthy controls (18) and positive skin atopy patch-test reactions to M. sympodialis have been found in AEDS patients (19).…”

TLR2/MyD88-Dependent and -Independent Activation of Mast Cell IgE Responses by the Skin Commensal Yeast Malassezia sympodialis

“…The lipophilic yeast Malassezia is part of the normal cutaneous flora but can elicit specific IgE and T cell reactivities in AE patients (6,7). The genus presently comprises 13 species (8,9) and Malassezia sympodialis is among the species most frequently isolated from both AE patients and healthy individuals (10).…”