Background
Pityrosporum folliculitis (PF) is an inflammatory skin disorder that typically manifests as a pruritic, follicular papulopustular eruption distributed on the upper trunk of young to middle-aged adults. Weary et al first described Pityrosporum folliculitis in 1969, and, later in 1973, Potter et al [1] identified Pityrosporum folliculitis as a separate clinical and histologic diagnosis. See the image below.
Left: A 25-year-old man with complaints of slightly pruritic, monomorphic follicular papules, pustules, and secondary keloid on the upper trunk and neck. Right: Scanning electron microscopy of the hair follicle from the upper trunk. This demonstrated a large number of globular or orbicular-ovate yeasts of budding daughter cell, with collar structure around the budding. Courtesy of Wikimedia Commons by Ran Yuping et al (https://commons.wikimedia.org/wiki/File:Pityrosporum_folliculitis_2.jpg).
Yeasts, specifically Malassezia furfur, are the pathogenic agents in Pityrosporum folliculitis. M furfur has been linked to several skin diseases, including seborrheic dermatitis, folliculitis, confluent and reticulated papillomatosis, and pityriasis versicolor. [2, 3] In 1874, Malassez first described round and oval budding yeasts from scales of patients with seborrheic dermatitis. He coined the phrases "bottle bacillus of Unna" to describe the small oval cells in the scale and "spore of Malassez" to name the bud that is observed in association with the yeast. Saborouraud proposed the Pityrosporum genus in 1904 to describe the budding yeast cells without hyphal elements from normal skin. Later, in the 1900s, Pityrosporum ovale and Pityrosporum orbiculare were isolated by Castellani and Chalmers and Gordon, respectively.
These 2 yeast species, collectively with fungal forms, are classified as M furfur because of controversy and confusion of the grouping of various lipophilic yeasts and fungi of the skin. This grouping has simplified the classification to one name, which applies regardless of the morphology of the organism. With the advancement of technology, 7 species of Malassezia were recognized: M furfur,Malassezia pachydermatous,Malassezia sympodialis,Malassezia globosa,Malassezia obtusa,Malassezia restricta, and Malassezia slooffiae. [4]
Pityrosporum folliculitis is caused by Malassezia species that are part of the cutaneous microflora and not by exogenous species. [5] However, the focus of this article is M furfur, which is considered the pathologic agent of Pityrosporum folliculitis. Lesions are chronic, erythematous, pruritic papules and pustules, which occur in a follicular pattern. These lesions are usually present on the back and chest and, occasionally, on the neck, shoulders, upper arms, and face.
The diagnosis of Pityrosporum folliculitis is based on clinical suspicion of the classic presentation of pruritic papulopustules found in a follicular pattern on the back, chest, upper arms, and, occasionally the neck. They are rarely present on the face. An improvement in the lesions with empiric antimycotic therapy supports a clinical diagnosis of Pityrosporum folliculitis.
Pathophysiology
M furfur (ie, P ovale and P orbiculare) is a lipophilic, saprophytic, budding, unipolar, dimorphic, gram-positive, double-walled, oval-to-round yeast. M furfur is part of the normal skin flora. It is suggested that the similar yeasts P orbiculare and P ovale are actually identical and that they are morphologic variants of M furfur.
Malassezia yeasts are classified as superficial mycoses that by definition do not invade past the cornified epithelium. In Pityrosporum folliculitis, however, the organism is present in the ostium and central and deep segments of the hair follicle.
Plugging of the follicle followed by an overgrowth of yeast that thrives in the sebaceous environment is believed to be the etiology. Malassezia yeasts require free fatty acids for survival. Usually, they are found in the stratum corneum and in pilar folliculi in areas with increased sebaceous gland activity such as the chest and back. The yeasts hydrolyze triglycerides into free fatty acids and create long-chain and medium-chain fatty acids from free fatty acids. The result is a cell-mediated response and activation of the alternative complement pathway, which leads to inflammation.
Etiology
Pityrosporum folliculitis is caused by Malassezia yeasts, which are lipophilic. Several factors can lead to changes in immunity, sebum production, and the growth of skin flora. These factors help to produce favorable conditions for growth of these yeasts.
Systemic diseases and pharmacologic agents that encourage the growth of yeast, possibly because of alterations in immunity, include the following:
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Diabetes mellitus
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Cushing disease
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Hodgkin disease [6]
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Cancer treated with cetuximab (IMC-C225; marketed under the name Erbitux), a chimeric (mouse/human) monoclonal antibody epidermal growth factor receptor (EGFR) inhibitor for the treatment of metastatic colorectal cancer and head and neck cancer [7]
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HIV infection
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Crohn disease treated with infliximab a monoclonal antibody against tumor necrosis factor alpha. [11]
An increase in sebum production, such as that in pregnancy, [12, 13] and high levels of androgens may potentiate the development of Pityrosporum folliculitis.
Antibiotics can alter normal skin flora, allowing the yeast to proliferate.
Pityrosporum folliculitis more frequently occurs in environments of high heat and humidity.
Occlusion of the skin and hair follicles with cosmetics, lotions, sunscreens, emollients, olive oil, or clothing creates favorable conditions for Pityrosporum folliculitis.
Anticonvulsant therapy and Down syndrome [14] are other conditions that are associated with Pityrosporum folliculitis.
Other related and coexisting conditions may include the following:
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Seborrheic dermatitis
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Confluent and reticulated papillomatosis
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Systemic candidiasis [15]
Some individuals seem to have an innate propensity for Pityrosporum folliculitis. In one experiment, Malassezia yeasts were applied to occluded forearm skin in patients with Pityrosporum folliculitis. Flares of Pityrosporum folliculitis occurred at the application site. In the same experiment, Pityrosporum folliculitis did not develop in patients with no prior diagnosis of the condition.
Epidemiology
Frequency
United States
Malassezia organisms can be found on the skin in 75-98% of healthy people. These organisms are part of the normal skin florae of many individuals who do not have signs or symptoms of folliculitis or other disease. Colonization by M furfur begins soon after birth, and the peak presence of the yeasts occurs in late adolescence and early adult life, coinciding with increasing activity of sebaceous glands and concentration of lipids in the skin.
International
P ovale is present on 90-100% of the surface of healthy skin; higher numbers of the yeast are present on the chest and back. Certain climates influence the percentage of people with P ovale and the number of people with Pityrosporum folliculitis. People living in warm and humid climates have a higher incidence of Pityrosporum folliculitis. One clinic in the Philippines documented that 16% of all patient visits were a result of Pityrosporum folliculitis. [16] A 2008 report from China cites that 1.5% off all dermatology patients were diagnosed with Pityrosporum folliculitis, most of them healthy, middle-aged males. [17]
Race
No known racial differences in the frequency of Pityrosporum folliculitis exist.
Sex
Reports of Pityrosporum folliculitis vary from a male-to-female ratio of 1:1 to a predominance of one or the other sex. More recent literature suggests that the female-to-male ratio might be a little higher. [18]
Age
Pityrosporum folliculitis is recognized as one that affects youths and young and middle-aged adults [19] ; Pityrosporum folliculitis is most common in those aged 13-45 years. However, 3 cases of Pityrosporum folliculitis occurred in an ICU setting in older individuals who were in consecutive beds, who received care from the same nursing staff, and who all received high-dose antibiotics. [20] . The very young can also be affected. [3]
Prognosis
The prognosis in Pityrosporum folliculitis is good. With treatment, Pityrosporum folliculitis can completely resolve. Without treatment, Pityrosporum folliculitis are classically pruritic.
Pityrosporum folliculitis may be a bothersome condition (ie, severe pruritus), but the lesions are benign. Some underlying conditions that predispose the patient to Pityrosporum folliculitis include diabetes mellitus, immunodeficiency, and systemic candidiasis [21] ; these conditions may cause morbidity. Consider the presence of predisposing conditions when Pityrosporum folliculitis is diagnosed.
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This photo is high-power hematoxylin and eosin staining of a biopsy confirming Pityrosporum folliculitis. There is a hair shaft within a hair follicle with scattered amphophilic staining circular Pityrosporum yeast. Courtesy of Ronald Rapini, MD.
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Left: A 25-year-old man with complaints of slightly pruritic, monomorphic follicular papules, pustules, and secondary keloid on the upper trunk and neck. Right: Scanning electron microscopy of the hair follicle from the upper trunk. This demonstrated a large number of globular or orbicular-ovate yeasts of budding daughter cell, with collar structure around the budding. Courtesy of Wikimedia Commons by Ran Yuping et al (https://commons.wikimedia.org/wiki/File:Pityrosporum_folliculitis_2.jpg).
