What is Malassezia Furfur?
Malassezia furfur is a type of fungus, or yeast, that’s typically found on human and animal skin. It is a part of a larger family of fungi, making up more than 80% of all yeast on our skin. It can be found on both healthy and diseased hosts. Some common skin disorders like seborrheic dermatitis (a common skin condition that mainly affects your scalp), pityriasis versicolor (a common skin condition caused by an overgrowth of yeast on the skin’s surface), and Malassezia folliculitis (an inflammatory skin condition caused by a yeast infection of the hair follicles) are often linked to Malassezia. There’s also emerging evidence suggesting that Malassezia might be contributing to other skin conditions such as atopic dermatitis (a type of inflammation of the skin) and psoriasis (a skin disease that causes red, itchy scaly patches). However, the exact role of these yeasts in causing these conditions is still under debate.
On another note, it’s important to mention that treatments reducing the number of Malassezia yeasts can lead to the improvement of some skin conditions. Particularly in patients with weakened immune systems, these yeasts can become opportunistic, leading to serious skin and systemic infections, or infections that spread throughout the body.
As early as 1846, scientists discovered a yeast associated with pityriasis versicolor, which was named Malassezia furfur in 1853. Recognized as a separate genus in 1889, since then, 17 different species of Malassezia have been found on human and animal skin. These are categorized based on their molecular structure, shape, phenotype (observable characteristics), and ultrastructure (fine detail). Among these species, M. globosa, M. restricta, and M. sympodialis are the most common types found on both healthy and diseased human skin. However, M. furfur is also widespread and has been closely linked to several skin disorders, particularly pityriasis versicolor. This summary will focus primarily on the most commonly related skin conditions to M. furfur – seborrheic dermatitis, pityriasis versicolor, and Malassezia folliculitis.
What Causes Malassezia Furfur?
M. furfur is a type of yeast that cannot produce its own fatty acids, which are oily substances needed for its growth. Instead, it relies on the oils produced by certain areas of our skin that are rich in oil-producing glands, known as sebaceous glands. These areas typically include the torso, face, and scalp.
While M. furfur is a common organism usually found on the outermost layer of our skin known as the stratum corneum, it doesn’t cause any issues for most people. However, problems can occur when this yeast changes into its more complex mycelial form. When this happens, it can lead to an infection.
Risk Factors and Frequency for Malassezia Furfur
M. furfur is a type of yeast that lives on the skin of most adults and even infants from 3 to 6 months old. It doesn’t prefer a specific age group or gender.
- Seborrheic dermatitis, or SD, affects 1 to 3% of all people. The rate would be higher if we counted milder cases like dandruff.
- The highest number of cases occur in patients with weaker immune systems – up to 33%.
- SD is more common in the winter months and has more male patients.
- The number of SD cases tends to spike in puberty and again after turning 50.
- SD is associated with various illnesses, including depression, HIV, Parkinson’s disease, and spinal injuries.
Pityrosporum ovale, or PV, commonly affects adults aged 20 to 50, when the sebaceous glands in the skin are most active. It’s particularly prevalent in the summer months and in tropical regions, where it affects nearly 40% of the population. In temperate regions, PV accounts for up to 3% of visits to dermatologists.
Malassezia folliculitis, a condition that causes skin inflammation, is more common in hot and humid climates. It is associated with weakened immune systems and often occurs alongside acne and other conditions caused by Malassezia, including SD and PV. In China, this condition accounts for about 1% to 1.5% of visits to dermatologists.
Recently, researchers have been comparing traditional culture-based methods and modern molecular techniques, like PCR, to study Malassezia populations. Each method has its advantages and disadvantages. While old-school methods can help identify specific harmful features of the yeast, molecular techniques excel in quick and precise detection and measurement of different Malassezia species. This new approach has proven helpful in isolating M. furfur in serious infections in patients with weakened immune systems and in premature babies in neonatal intensive care units who receive nutrition through catheters. Though these techniques show a lot of promise, they’re not used in the clinic just yet.
Signs and Symptoms of Malassezia Furfur
Seborrheic Dermatitis (SD) is a condition often showing as red, oily patches with flaky scales. These patches usually appear on the scalp, around the nose, eyebrows, and chest. It’s less severe form is known as dandruff which appears as red, oily, itchy and scaly patches on the scalp. In children, it often resolves on its own, mainly affecting the scalp and is commonly known as “cradle cap”.
Pityriasis Versicolor (PV) is a skin condition showing as round to oval skin marks, patches, or plaques that change in color, hence its name. These spots vary from under-pigmented (lighter than the skin) to over-pigmented (darker than the skin) and may be red, blue, pink, or grey. These lesions may have scaling around their edges and cause itching.
Malassezia folliculitis can appear similar to acne with red bumps and pus-filled bumps which may be itchy. Some studies report a common presentation as dome-shaped, comedopapules (skin bumps) with a central “dell” similar to a skin condition named Molluscum Contagiosum. Patients affected by this are often in intensive care or have compromised immune systems due to biologic agents or chemotherapy treatment.
In patients with weakened immune systems, the clinical signs of fungemia (fungus in the blood) and sepsis are not specific. These patients are typically critically ill and may suddenly start experiencing fevers, chills, lethargy, and signs and symptoms of internal organ damage. Fungal organisms can enter the bloodstream through medical devices like central venous catheters or parenteral lines (tubes that deliver nutrients directly into the body).
Testing for Malassezia Furfur
Usually, most conditions related to the fungus Malassezia furfur are diagnosed based on symptoms observed by the doctor. But, because symptoms can vary a lot and might resemble other diseases, a microscopic test using a special solution called KOH can assist in the identification of skin disorders caused by this type of fungus.
In some cases, when treatment is not working as expected, or when there is uncertainty about the diagnosis, it might be necessary to take a small sample (biopsy) from skin disorders such as Malassezia folliculitis (a type of acne) and psoriasis (a skin condition that causes red, flaky, crusty patches of skin).
For a skin condition known as Pityriasis versicolor (PV), a special lamp known as a Wood’s light might be used to help with the diagnosis. This lamp can make areas of the skin affected by the M. furfur fungus glow in a yellow-gold color. However, this method only works in about a third of cases.
Diagnosing a bloodstream infection caused by this fungus is tricky and needs a high degree of suspicion. Simple microscopic tests using a special dye called Giemsa can easily detect the yeast form of this fungus. But, when you need to grow the fungus in a lab for identification, it can be quite challenging and time-consuming.
Recently, new techniques for diagnosis using molecular methods have been developed, but these are not widely available for clinical use yet.
Treatment Options for Malassezia Furfur
Malassezia is a type of yeast that is often involved in certain skin conditions like seborrheic dermatitis (SD), pityriasis versicolor (PV), and a condition referred to as Malassezia folliculitis.
To treat these conditions, doctors usually use products like shampoos or creams that contain certain ingredients. These may include selenium and zinc salts, propylene glycol, and compounds with sulfur. They have properties that can control inflammation and are capable of breaking down the hard layer of skin cells where this yeast tends to grow. Specific antifungal medicines, like azoles or terbinafine, are also used to directly combat the yeast.
If the skin condition is severe, more extensive, or if hasn’t responded well to other treatments, oral antifungals might be used. However, oral terbinafine is not as effective as the topical form for treating PV. In the past, creams or oral tablets containing corticosteroids were used for SD. However, other options, such as antifungal treatments like topical tacrolimus and pimecrolimus, have shown good results.
In treating SD, the main goal is to limit the growth of the Malassezia yeast and to control the resulting skin inflammation. Typical first-line treatments include products specifically designed to stop the growth and spread of the yeast or kill it entirely, such as topical antifungals or corticosteroids. Other commonly used ingredients include zinc pyrithione, selenium sulfide, and ciclopirox olamine. They are available in various forms like shampoos, creams, and gels. They are chosen for their ability to control inflammation, break down the hard layer of skin cells, and combat yeast.
Topical antifungal treatments, which can be found in shampoos, are also highly effective and generally well-received by patients. Azoles like ketoconazole and fluconazole are commonly used. For more stubborn cases of SD, the patient might require more aggressive treatment such as oral ketoconazole or itraconazole. A similar treatment strategy is followed when it comes to treating PV.
There are options for systemic antifungal therapy (i.e., medication given through the mouth or injected into the bloodstream) for more severe cases or when the disease doesn’t respond to topical treatments. They can be used alone or in combination with other treatments. This same therapeutic approach could also work for Malassezia folliculitis.
In rare cases, Malassezia can result in a more serious, invasive infection. In such instances, a healthcare team might recommend removing any central venous catheters (a long, thin tube that’s inserted into a large vein, usually in the neck, chest, or groin) because the yeast can create a film over these catheters. As there isn’t much solid scientific evidence to guide the management of these rare instances, doctors tend to use therapies that have been seen to be effective in smaller-scale studies. These include treatments like the antifungal triazoles and a medication called amphotericin B. The patient might first be given these medications intravenously (into a vein), then change to an oral form after around two weeks.
What else can Malassezia Furfur be?
When diagnosing Seborrheic Dermatitis (SD), doctors should take other skin conditions into account, especially if symptoms don’t resolve with treatment or if the patient’s condition differs from the usual SD symptoms. Here are some similar conditions:
- Psoriasis: It usually appears as more red skin with heavy silvery scaling. The patches are clearly marked and family history may be relevant.
- Rosacea: This shows up as redness and pimples on the nose and areas around the mouth and eyes, but without scaling.
- Atopic Dermatitis or Eczema: It needs consideration, especially when seeming SD isn’t improving with treatment. Intense itching may make it different from SD.
- Secondary syphilis: It also mimics other skin diseases, so testing is important if suspicion is high.
- Systemic Lupus Erythematosus (SLE): It may also present with redness on cheeks, but unlike SD it doesn’t affect nasolabial folds or cross the bridged nose.
- Pemphigus Foliaceous: This involves red patches on the head, scalp and trunk characterized by scaling and pain.
- In children: Tinea infections and diaper rash should also be considered.
Similarly, diagnosing Pityriasis Versicolor (PV) involves considering diseases like:
- SD: It can also occur on the trunk. But its skin lesions are more red with heavy scaling.
- Pityriasis rosea: It can be distinguished with the appearance of a leading patch before symptoms, “Christmas tree” distribution, and red, scaling skin patches.
- Vitiligo: It can be differentiated from PV due to lack of pigmentation.
- Secondary syphilis: It must be ruled out when there are hyperpigmented spots on the palms and soles.
- Mycosis fungoides: It typically shows up as patches on the trunk and extremities.
Finally, don’t forget that conditions like bacteria, fungi, and viruses can cause folliculitis:
- Herpes simplex and papillomavirus folliculitis: They are identified by blisters on a red base and centered pimples, respectively.
- Bacterial and fungal folliculitis: They may show up as painful, itching hair follicle inflammation and pus-filled bumps. Detailed patient history and diagnostic tests can help confirm diagnosis.
- The presence of plugged pores and the absence of itching suggest acne vulgaris rather than Malassezia folliculitis.
What to expect with Malassezia Furfur
Skin conditions that are associated with M. furfur, a type of yeast, can often be chronic, meaning they persist over a long time, and relapsing, meaning they come back after treatment. Those with a weakened immune system have a higher chance of these conditions returning. Furthermore, certain environmental factors can make the symptoms worse or better. For instance, cold weather tends to worsen Seborrheic Dermatitis (SD), a common skin condition that mainly affects the scalp, while Pityriasis Versicolor (PV), a fungal infection that causes small patches of skin to become scaly and discolored, is more commonly seen in the summer.
Generally, PV responds well to creams, lotions, or shampoos that are applied to the skin, although the changes in skin color that result from the infection might take several months to return to normal.
Possible Complications When Diagnosed with Malassezia Furfur
Most skin disorders caused by M. furfur are usually mild. However, these disorders can affect a person’s appearance, leading to social stigma and emotional distress. It is important to note that these conditions can also lead to secondary bacterial and viral infections, often complicating Seborrheic Dermatitis (SD) and atopic dermatitis (a type of skin rash). In rare but serious instances, the normal bacteria on the skin can get into the bloodstream (called fungemia). This can cause a systemic infection, particularly in patients with weakened immune systems.
Common Issues:
- Mild skin disorders
- Changes in appearance
- Social stigma
- Emotional distress
- Secondary bacterial and viral infections
- Complications with Seborrheic Dermatitis and Atopic Dermatitis
- Rare but serious systemic infection (fungemia), especially in immunosuppressed patients
Preventing Malassezia Furfur
Patients should know that M. furfur is a type of yeast that commonly lives on human skin and does not usually cause any problems. However, it can sometimes lead to certain skin conditions such as SD (seborrheic dermatitis), PV (pityriasis versicolor), and Malassezia folliculitis. These conditions are harmless and cannot be passed from person to person.
The way these skin conditions look and feel can differ greatly from person to person. For instance, PV might cause skin patches that vary in color depending on whether the person has light or dark skin. This condition often gets worse in hot and humid weather. To be sure if someone has PV, a doctor has to look at a sample of the person’s skin under a microscope.
The usual treatment involves using special shampoos or creams, or sometimes pills if the condition covers a large area of the body. Regular use of the shampoo can help prevent future flare-ups. If a patient experiences a lot of itching, the doctor might suggest over-the-counter or prescription medications to help relieve this.
