What is Malassezia (Pityrosporum) folliculitis?

Updated: Apr 03, 2020
  • Author: Sarah Sweeney Pinney, MD, FAAD; Chief Editor: William D James, MD  more...
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Answer

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 slightl 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.


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