Introduction
Malassezia furfur is a type of fungus (yeast) that naturally resides on the skin surfaces of humans and some mammals and forms a part of the physiological flora of the skin. This fungal species has been found to be associated with several skin conditions, causing various skin manifestations. Research has shown that Malassezia is also associated with rare cases of fungemia and systemic infections.
What Is Malassezia Furfur?
Malassezia furfur is a genus of fungi that naturally lives on the skin surfaces of humans and animals. It is a commensal organism that lives on the superficial surface of the dermis, forming the natural flora of the skin. A commensal organism refers to a member of the species that receive benefits from the other organism without causing harm or benefits. Malassezia is a lipid-dependent yeast that constitutes more than 80 percent of the total fungal population of human skin and is often seen in both healthy and diseased hosts. It is associated with several skin conditions caused by fungal infections, specifically tinea versicolor and seborrhoeic dermatitis. Among the species of Malassezia, M. globosa, M. restricta, and M.sympodialis are the common types found on the skin of healthy and diseased hosts. M.furfur is also prevalent, but studies have shown that it is specifically seen in multiple skin disorders.
What Are the Characteristics of Malassezia Furfur?
Malassezia furfur is a commensal organism that lives on the skin surfaces of humans and animals. It forms the physiological flora, and it colonizes adults and infants by three to six months of life. Malassezia does not have any age or sex predilection. Though it forms the natural flora of the skin, it can become pathogenic when it morphs from yeast to hyphae (cylindrical filaments) during its life cycle. These changes are due to unknown molecular changes, which can result in uncontrolled proliferation of Malassezia and an imbalance in the residential flora of the skin. Some virulence factors can increase the ability of the fungus to acquire an infectious nature, which includes the formation of biofilms, increased adherence potential, and the ability to form hyphae.
The pathogenic Malassezia furfur can cause infections on the trunk or the limbs, which present as pigmented macules (flat, distinct discoloration on the skin) that merge in the form of plaques. However, most of these lesions resolve spontaneously. The pathogenic form frequently affects children more than people of other age groups. Malassezia furfur is associated with a variety of skin conditions, including tinea circinata, pityriasis versicolor, seborrhoeic dermatitis, and dandruff. It is also associated with other conditions, such as catheter-related fungemia (the presence of fungi or yeasts in the blood) and pneumonia (inflammation of the alveoli of the lungs) in patients receiving hematopoietic cell transplants.
How Does Malassezia Furfur Affect the Skin?
The exact pathophysiology of Malassezia species has not been established. However, pityriasis versicolor, a superficial fungal infection, may involve a high fungal load without inflammation, whereas atopic dermatitis, seborrhoeic dermatitis, psoriasis, and Malassezia folliculitis are characterized by inflammation. This disease manifests as a multifactorial disorder involving environmental and genetic factors, the host immune system interactions, and yeast enzymatic actions on the skin. In addition, the colonization of Malassezia exacerbates the existing dermatoses and also acts opportunistically in immunocompromised individuals.
What Are the Signs and Symptoms of Skin Disorders Associated With Malassezia Furfur?
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Seborrhoeic Dermatitis - The clinical manifestations associated with seborrhoeic dermatitis include varying degrees of erythematous (red), greasy, and flaky plaques that predominantly affect the chest, eyebrows, scalp, and nasolabial folds. In addition, dandruff is also seen with red, oily, and scaly patches that are itchy (pruritic). This condition is typically self-limited in children, and scalp involvement is common, so it is referred to as cradle cap.
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Pityriasis Versicolor - The clinical manifestations of pityriasis versicolor include multiple rounds to oval macules, plaques, or patches that vary in color. Hence it is called versicolor. The discoloration ranges from a hypopigmented lesion to a hyperpigmented lesion that is blue, pink, red, or grey. These lesions may develop pruritis and peripheral scaling.
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Malassezia Folliculitis - The signs and symptoms of Malassezia folliculitis may present similar to acne as pustules (red bumps filled with white pus at their tips) and erythematous papules (solid red bumps that do not have pus-filled tips) with or without pruritis. These lesions are dome-shaped papules, unlike molluscum contagiosum. Patients affected with this condition often require hospitalization.
In immunocompromised patients, the clinical manifestations of sepsis and fungemia associated with Malassezia are not specific. These patients are usually critically ill and develop sudden fever, chills, lethargy, and symptoms of internal organ involvement as yeasts may gain access to veins through parenteral lines or central venous catheters. Hence, central venous catheters should not be used in invasive Malassezia infection.
How Are Conditions Associated With Malassezia Furfur Diagnosed?
The diagnosis of skin conditions associated with Malassezia furfur depends on clinical findings. As these clinical features are similar to other diseases, microscopic examination is recommended for these skin disorders. Malassezia folliculitis and psoriasis may require a biopsy if they are refractory to treatment. Wood’s light technique that induces yellow-gold fluorescence may aid in the diagnosis of lesions associated with Malassezia furfur. Recent advancement includes molecular diagnostic methods, but are not yet available for clinical use.
How Are Skin Disorders Associated With Malassezia Furfur Treated?
The main aim of treatment is to reduce the proliferation of Malassezia, and the resulting inflammatory response. The treatment involves the use of topical antifungals or corticosteroids. Malassezia species are susceptible to oral and topical agents with anti-inflammatory, keratolytic, and antifungal properties. Creams and shampoos containing zinc salts and selenium, propylene glycol, and compounds with sulfur are effective against Malassezia species. Topical treatment with antifungals like Azoles and Terbinafine is also effective. The severe diffuse or recalcitrant disorder requires oral antifungal therapy. Seborrhoeic dermatitis is treated with topical and oral corticosteroids and antifungals. Pityriasis versicolor treated with topical terbinafine shows promising results.
Conclusion
Malassezia furfur is a type of fungus (yeast) that is associated with various skin conditions. However, in a majority of cases, the skin disorders caused by Malassezia furfur are relatively benign. These skin disorders can be effectively treated with antifungals, but recurrence is possible. If any symptoms of redness, itching, or scaly patches on the skin are seen, it is essential to consult a dermatologist. With proper care and management, Malassezia furfur can be treated well.
