Module 1.3 Patches and Plaques
MALASSEZIA
Fitzpatrick’s Dermatology in General Medicine [9E]
AT-A-GLANCE ● Malassezia species are normal cora of human skin.
● Malassezia species can produce a variety of clinical presentations including pityriasis (tinea) versicolor,
Malassezia folliculitis, seborrheic dermatitis, and neonatal cephalic pustulosis. Rarely, Malassezia species
have been implicated in systemic infections, including catheter-related fungemia.
● The diagnosis can be made via potassium hydroxide (KOH) preparation or skin biopsy. The organism is not
typically cultured for this purpose as it requires special growing conditions (additional lipid).
● Malassezia skin infections generally respond readily to topical treatments, including azole antifungals and
selenium sulfide–based preparations. More extensive cases or those with folliculitis may require systemic
antifungals.
● Malassezia infections tend to have high recurrence rates and may require prophylactic treatment to prevent
further episodes.
EPIDEMIOLOGY Malassezia Overview:
● Malassezia (formerly Pityrosporum) are lipophilic, dimorphic fungi.
● Associated with skin conditions like pityriasis (tinea) versicolor and Malassezia folliculitis.
● Linked to inflammatory skin conditions such as seborrheic dermatitis and atopic dermatitis, though their role
is unclear and possibly exacerbatory rather than infectious.
Species & Colonization:
● There are 14 known species in the Malassezia genus, 11 of which are commensals on human skin.
● Colonization typically occurs between 3 to 6 months of age.
● Earlier colonization is associated with longer neonatal intensive care unit (NICU) stays.
Epidemiology & Risk Factors:
● Malassezia infections are more common in tropical climates and during adolescence to young adulthood,
corresponding with peak sebum production.
● Pityriasis Versicolor & Malassezia Folliculitis: Malassezia globosa is the most commonly isolated
species. Other frequently isolated species include Malassezia restricta and Malassezia sympodialis.
Other Infections:
● Malassezia species (primarily M. restricta and M. globosa) have been isolated from the sinuses of both
healthy individuals and patients with chronic rhinosinusitis.
● Implicated in various internal infections such as urinary tract infections, meningitis, pneumonia, and
nosocomial bloodstream infections.
Catheter-Related Fungemia:
● Most commonly caused by Malassezia pachydermatis, especially in neonates (preterm infants receiving
parenteral lipid infusions and prolonged vascular catheterization).
● Malassezia fungemia is also reported in older children and adults who are immunocompromised (e.g.,
leukemia, solid tumors, diabetes, severe combined immunodeficiency), often with indwelling catheters and
not receiving lipid infusions.
,CLINICAL FEATURES Pityriasis (Tinea) Versicolor:
● A superficial infection caused by Malassezia, predominantly affecting adolescents and young adults.
● Often referred to as "tinea versicolor," though unlike other "tinea" infections caused by dermatophytes, this
is caused by yeast.
● Symptoms:
○ Asymptomatic or mildly itchy (pruritic) patches and thin plaques with a fine, overlying scale.
○ Lesions primarily appear on the neck, chest, back, and upper arms.
○ Less commonly, lesions can be found on the scalp, abdomen, and groin.
● Skin Color Changes ("Versicolor"):
○ Skin color changes include hypopigmentation, hyperpigmentation, and erythematous to
salmon-colored lesions.
Malassezia Folliculitis:
● Presents as erythematous, monomorphic papules and pustules centered around hair follicles.
● Commonly affects the face, trunk, and upper arms.
● Distinct Features:
○ Unlike acne vulgaris, comedones are absent.
○ Typically spares the centrofacial area (unlike acne).
● Lesions are often pruritic but not always.
● Frequently misdiagnosed as acne vulgaris and can co-occur with acne.
ETIOLOGY AND PATHOGENESIS Malassezia as Normal Flora:
● Malassezia are part of the normal skin flora and rely on host sebum triglycerides for survival as they lack
the ability to synthesize C14-C16 saturated fatty acids.
● They hydrolyze sebum triglycerides, releasing free fatty acids, which are believed to provoke skin
inflammation.
Pathogenesis:
● In pityriasis versicolor, Malassezia transitions to its pathogenic mycelial form and invades the stratum
corneum.
● Pigmentary changes in the skin occur via multiple mechanisms:
○ Hypopigmentation: Caused by the production of azelaic acid, which inhibits tyrosinase (key
, enzyme in melanin synthesis) and may be cytotoxic to melanocytes.
○ Hyperpigmentation: Results from increased melanosomes and thickening of the stratum corneum.
Risk Factors:
● Increased rates of pityriasis versicolor and Malassezia folliculitis are linked to tropical climates and
heavy sweating.
● Other risk factors for Malassezia folliculitis include:
○ Immunosuppression
○ Use of oral antibiotics
○ Use of corticosteroids
● No consistent gender predilection has been observed.
DIAGNOSIS Supportive Studies:
● Visual Diagnosis: Pityriasis versicolor is often identified visually due to its distinctive appearance.
● Dermoscopy: Useful as an ancillary tool, especially to highlight the fine scaling that may not always be
visible to the naked eye.
● Wood Lamp: May reveal a yellow-green fluorescence in both pityriasis versicolor and Malassezia
folliculitis.
● KOH Preparation: Reveals short hyphae and yeast forms (referred to as the "ziti and meatballs" sign).
○ For pityriasis versicolor, a superficial skin scraping is adequate.
○ For Malassezia folliculitis, using a comedone extractor or needle to puncture a pustule is
recommended to obtain a deeper specimen.
○ Calcofluor white or May-Grunwald-Giemsa stains can improve visualization of the organism.
Laboratory Testing:
● Culture: Not commonly used due to Malassezia's lipid requirement, making culture technically challenging.
○ Requires a layer of olive oil or special growth media like modified Dixon.
○ Different Malassezia species have slightly different growth requirements.
Pathology:
● Pityriasis Versicolor: Malassezia yeast forms are typically found in the stratum corneum.
● Malassezia Folliculitis: Yeast forms are found in dilated infundibula of plugged follicles along with keratin
debris.
● A mild perivascular inflammatory infiltrate consisting of lymphocytes, histiocytes, and neutrophils may be
seen, with increased inflammation if a follicle has ruptured.
● Periodic Acid–Schiff (PAS) Stain: Can highlight the presence of Malassezia organisms.
MALASSEZIA
Fitzpatrick’s Dermatology in General Medicine [9E]
AT-A-GLANCE ● Malassezia species are normal cora of human skin.
● Malassezia species can produce a variety of clinical presentations including pityriasis (tinea) versicolor,
Malassezia folliculitis, seborrheic dermatitis, and neonatal cephalic pustulosis. Rarely, Malassezia species
have been implicated in systemic infections, including catheter-related fungemia.
● The diagnosis can be made via potassium hydroxide (KOH) preparation or skin biopsy. The organism is not
typically cultured for this purpose as it requires special growing conditions (additional lipid).
● Malassezia skin infections generally respond readily to topical treatments, including azole antifungals and
selenium sulfide–based preparations. More extensive cases or those with folliculitis may require systemic
antifungals.
● Malassezia infections tend to have high recurrence rates and may require prophylactic treatment to prevent
further episodes.
EPIDEMIOLOGY Malassezia Overview:
● Malassezia (formerly Pityrosporum) are lipophilic, dimorphic fungi.
● Associated with skin conditions like pityriasis (tinea) versicolor and Malassezia folliculitis.
● Linked to inflammatory skin conditions such as seborrheic dermatitis and atopic dermatitis, though their role
is unclear and possibly exacerbatory rather than infectious.
Species & Colonization:
● There are 14 known species in the Malassezia genus, 11 of which are commensals on human skin.
● Colonization typically occurs between 3 to 6 months of age.
● Earlier colonization is associated with longer neonatal intensive care unit (NICU) stays.
Epidemiology & Risk Factors:
● Malassezia infections are more common in tropical climates and during adolescence to young adulthood,
corresponding with peak sebum production.
● Pityriasis Versicolor & Malassezia Folliculitis: Malassezia globosa is the most commonly isolated
species. Other frequently isolated species include Malassezia restricta and Malassezia sympodialis.
Other Infections:
● Malassezia species (primarily M. restricta and M. globosa) have been isolated from the sinuses of both
healthy individuals and patients with chronic rhinosinusitis.
● Implicated in various internal infections such as urinary tract infections, meningitis, pneumonia, and
nosocomial bloodstream infections.
Catheter-Related Fungemia:
● Most commonly caused by Malassezia pachydermatis, especially in neonates (preterm infants receiving
parenteral lipid infusions and prolonged vascular catheterization).
● Malassezia fungemia is also reported in older children and adults who are immunocompromised (e.g.,
leukemia, solid tumors, diabetes, severe combined immunodeficiency), often with indwelling catheters and
not receiving lipid infusions.
,CLINICAL FEATURES Pityriasis (Tinea) Versicolor:
● A superficial infection caused by Malassezia, predominantly affecting adolescents and young adults.
● Often referred to as "tinea versicolor," though unlike other "tinea" infections caused by dermatophytes, this
is caused by yeast.
● Symptoms:
○ Asymptomatic or mildly itchy (pruritic) patches and thin plaques with a fine, overlying scale.
○ Lesions primarily appear on the neck, chest, back, and upper arms.
○ Less commonly, lesions can be found on the scalp, abdomen, and groin.
● Skin Color Changes ("Versicolor"):
○ Skin color changes include hypopigmentation, hyperpigmentation, and erythematous to
salmon-colored lesions.
Malassezia Folliculitis:
● Presents as erythematous, monomorphic papules and pustules centered around hair follicles.
● Commonly affects the face, trunk, and upper arms.
● Distinct Features:
○ Unlike acne vulgaris, comedones are absent.
○ Typically spares the centrofacial area (unlike acne).
● Lesions are often pruritic but not always.
● Frequently misdiagnosed as acne vulgaris and can co-occur with acne.
ETIOLOGY AND PATHOGENESIS Malassezia as Normal Flora:
● Malassezia are part of the normal skin flora and rely on host sebum triglycerides for survival as they lack
the ability to synthesize C14-C16 saturated fatty acids.
● They hydrolyze sebum triglycerides, releasing free fatty acids, which are believed to provoke skin
inflammation.
Pathogenesis:
● In pityriasis versicolor, Malassezia transitions to its pathogenic mycelial form and invades the stratum
corneum.
● Pigmentary changes in the skin occur via multiple mechanisms:
○ Hypopigmentation: Caused by the production of azelaic acid, which inhibits tyrosinase (key
, enzyme in melanin synthesis) and may be cytotoxic to melanocytes.
○ Hyperpigmentation: Results from increased melanosomes and thickening of the stratum corneum.
Risk Factors:
● Increased rates of pityriasis versicolor and Malassezia folliculitis are linked to tropical climates and
heavy sweating.
● Other risk factors for Malassezia folliculitis include:
○ Immunosuppression
○ Use of oral antibiotics
○ Use of corticosteroids
● No consistent gender predilection has been observed.
DIAGNOSIS Supportive Studies:
● Visual Diagnosis: Pityriasis versicolor is often identified visually due to its distinctive appearance.
● Dermoscopy: Useful as an ancillary tool, especially to highlight the fine scaling that may not always be
visible to the naked eye.
● Wood Lamp: May reveal a yellow-green fluorescence in both pityriasis versicolor and Malassezia
folliculitis.
● KOH Preparation: Reveals short hyphae and yeast forms (referred to as the "ziti and meatballs" sign).
○ For pityriasis versicolor, a superficial skin scraping is adequate.
○ For Malassezia folliculitis, using a comedone extractor or needle to puncture a pustule is
recommended to obtain a deeper specimen.
○ Calcofluor white or May-Grunwald-Giemsa stains can improve visualization of the organism.
Laboratory Testing:
● Culture: Not commonly used due to Malassezia's lipid requirement, making culture technically challenging.
○ Requires a layer of olive oil or special growth media like modified Dixon.
○ Different Malassezia species have slightly different growth requirements.
Pathology:
● Pityriasis Versicolor: Malassezia yeast forms are typically found in the stratum corneum.
● Malassezia Folliculitis: Yeast forms are found in dilated infundibula of plugged follicles along with keratin
debris.
● A mild perivascular inflammatory infiltrate consisting of lymphocytes, histiocytes, and neutrophils may be
seen, with increased inflammation if a follicle has ruptured.
● Periodic Acid–Schiff (PAS) Stain: Can highlight the presence of Malassezia organisms.
