Malassezia - clinical and immunological aspects
Malassezia sympodialis as well as Malassezia furfur are yeasts that frequently trigger allergies in patients with atopic dermatitis. Areas such as the head and neck are preferred habitats.
Atopic eczema is one of the most common chronic skin diseases and the result of a complex interaction of genetic and environmental factors. Essentially, the epidermal barrier defect that underlies atopic eczema is due to a mutation in the filaggrin gene. This skin barrier defect facilitates the entry of microbes and allergens. Malassezia yeasts are part of the normal microflora of the skin and require a high skin lipid content for growth, which explains the increased Malassezia colonisation in exceptional hormonal situations such as puberty. Certain Malassezia species are capable of producing allergens that promote inflammation of the skin, thus initiating a kind of "inflammatory cycle" in atopic eczema. Malassezia fungal spores sensitise directly through the skin, which can be detected by allergy tests (blood tests or skin tests). It has been shown that sensitisation to Malassezia correlates with the severity of skin disease. Both the production of specific IgE and the stimulation of T-lymphocytes are probably also related to the fact that the skin barrier is disturbed in atopic eczema - the skin is extremely dry then.
Malassezia species are also present on the skin of healthy people, but they cannot penetrate deeply because the skin barrier is intact. In atopic eczema, the skin barrier is disturbed, which enables Malassezia yeast fungi or their components or allergens to enter the skin and thus come into contact with the immune system. This then leads to IgE and T cell stimulation.
The importance of early Malassezia detection
IgE-mediated Malassezia sensitisation has been found in up to 49% of patients with atopic dermatitis, most commonly in men and in the head and neck area. (1) Children are much less commonly affected due to age-dependent exposure conditions to Malassezia. The correlation with disease activity underlines the prognostic importance of detecting specific IgE antibodies against Malassezia yeasts in the blood of patients with atopic dermatitis.
Precise serological clarification with ALEX2® possible
The ALEX2® multiplex test includes the most important Malassezia allergens, such as Mala s 5, 6 and 11.
Mala s 5 is a member of the redoxin allergen family. The degree of cross-reactivity with other members of this allergen family (in moulds and yeasts) is moderate. 23 out of 97 (24%) patients with atopic dermatitis react positively to Mala s 5 in the skin test. (2)
Mala s 6 is a member of the cyclophilin allergen family. The degree of cross-reactivity with other members of this family is high. 20 of 97 (21%) atopic eczema patients had positive SPT results to rMala s 6. (2, 3)
Mala s 11 is a member of the Mn-superoxide dismutase allergen family. The degree of cross-reactivity with other members of this allergen family is high. Mala s 11 can induce autoreactive T cells. The importance of this allergen in atopic dermatitis (AD) was supported by a strong correlation between the severity of AD and sensitisation to Mala s 11. 75% of 28 atopic dermatitis patients had IgE to rMala s 11 by ELISA. (4)
The basis for therapy is consistent skin care. In the case of clinically manifest skin inflammation in AD episodes, anti-inflammatory treatment is necessary. AD patients may benefit from antifungal therapy, which is effective against Malassezia.
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- doi: 10.1111/j.1432-1033.2004.04098.x