What is the pathophysiology of 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

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.


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