Pityrosporum folliculitis

Pityrosporum folliculitis (PF) is a common benign disorder in young or middle-aged adults that involves follicular papules and pustules localized predominantly on the back and chest. As the name suggests, Malassezia folliculitis is caused by the invasion of the hair follicle by Malassezia yeasts. Although Malassezia yeasts are a part of the normal human microflora, under certain conditions they can cause superficial dermatological conditions. The invasion results in the development of erythematous papules, and sometimes pustules, which may be either asymptomatic or itchy. Usually Malassezia yeasts are present along with staphylococci and propionibacteria in the follicles.

Malassezia are lipophilic (requiring the presence of lipid substances for their development, in either skin sebum or culture media) yeasts commonly found on skin and body surfaces of humans and animals. There are seven proposed species in the genus Malassezia based on molecular, morphological, and biochemical profiles.

Their variable morphology and the difficulty in isolating and maintaining them in culture have brought about a long-lasting controversy on the role of the Malassezia yeasts in various skin conditions. During the past two decades, this group of yeasts has gained increasing importance, and great progress has been made in defining the ecology and implicit role of the different species in associated pathological disorders. The nomenclature too has been changed, newer species have been identified and associations of the organism with different disease entities have been studied and documented.

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 osteum and central and deep segments of the hair follicle. All the species have distinct morphological characteristics, which allow them to be differentiated from other yeasts. The cells are round, oval or cylindrical, depending on the species. The reproduction of Malassezia is asexual with unipolar budding, the daughter cells being formed successively in a single locus, leaving a prominent scar on the mother cell. Some species may develop pseudomycelium in vivo as well as in vitro.

Malassezia yeasts require free fatty acids to survive. The yeasts hydrolyze triglycerides into free fatty acids and create long-chain and medium-chain fatty acids from free fatty acids, resulting in a cell-mediated response, which leads to inflammation. Because of their dependence on lipids for survival, Malassezia yeasts are found in sebum rich areas of the body such as the trunk, back, face and scalp.

The pathogenic agents identified in Pityrosporum folliculitis are yeasts from the genus Pityrosporum–Pityrosporum orbiculare and Pityrosporum ovale, which are collectively known as Malassezia furfur. It is not clear whether the organism plays a pro-active causative role or whether there is merely a proliferation of Malassezia in the enlarged follicle. However, direct microscopy and histopathology show that there is a definite and clear pattern of colonization of hair follicles by Malassezia yeasts. The role of Malassezia yeast in pityrosporum folliculitis is further endorsed by the fact that topical antifungal treatment is effective in most cases.

Malassezia folliculitis is more frequently observed in tropical countries and in summer in temperate regions. Occlusion (as in wearing a hat so that the sclap skin get humid) seems to be one of the causative agents this disorder. The condition has also been reported in patients undergoing treatment with broad-spectrum antibiotics like tetracyclines and with corticosteroids. Cases of Malassezia folliculitis in heart transplant recipients receiving immunosuppressive treatment have also been documented. Another predisposing factor of Pityrosporum folliculitis is diabetes mellitus.

Similar to other skin conditions associated with invasion by Malassezia yeasts, the development of Malassezia folliculitis appears to have an immune component, and has been reported to occur in immunosuppressed individuals. Moreover, the eosinophilic folliculitis seen in patients with HIV and AIDS may also be marked by colonization of the follicles with Malassezia yeasts.

Studies by some authors observing the condition in a tropical climate observe that the humid and hot climate of the tropics may provoke more severe cases of Malassezia folliculitis than tend to occur in more temperate regions. These authors claim that Malassezia folliculitis is actually a polymorphic disorder. They describe the most common lesion as a molluscoid, dome-shaped comedopapule (2-3 mmin diameter) with a central “dell” representing the follicle. However, they also report that in severe cases, patients may also have pustules, nodules, and cysts.

Pityrosporum folliculitis clinical features

The classic presentation of Pityrosporum folliculitis is a follicular pattern of papulopustules. Tiny dome-shaped pink papules and small superficial pustules arise in crops on the upper back, shoulders and chest. In some geographic regions, particularly humid and tropical areas, it can occasionally affect other areas including the neck, face and upper arms. The diagnosis is based largely on clinical suspicion and with either demonstrable M furfur yeast forms or an improvement in the lesions with empiric anti-yeast therapy.

Pityrosporum folliculitis pathology

Several culture-based and molecular techniques have been designed to distinguish the Malassezia species. In most cases of folliculitis, if a biopsy specimen of affected hair follicles is cut in serial sections, a typical dilated follicle will contain abundant round budding yeast cells and sometimes hyphae will also be found. Also, the organism is seen on direct microscopic examination, usually in the absence of other micro-organisms. These arguments strongly support the pathogenic role of Malassezia in this disease.

Histological features of Malassezia folliculitis include the presence of an inflammatory infiltrate consisting of lymphocytes, histiocytes (A relatively inactive, immobile macrophage found in normal connective tissue), and neutrophils (granular leukocytes having a multi-lobed nucleus), along with focal rupture of the follicular epithelium. Spherical and budding yeast cells have been identified as well as the presence of circulating IgG antibodies against P. ovale in high titers.

The hair follicles tend to be dilated and distended and are often full of keratinous material. It has also been suggested that the overgrowth of the yeasts is a secondary occurrence, permitted by the occlusion of the follicle.

Pityrosporum folliculitis differential diagnosis

Although Pityrosporum folliculitis is a common condition, it is often misdiagnosed as acne. Experienced clinicians would be aware that pruritis and the absence of comedones (blackheads) and facial lesions distinguish Pityrosporum folliculitis from acne.

Pityrosporum folliculitis treatment

Most infectious diseases seen by dermatologists and clinicians can be successfully managed if the true etiology of the patients’ dermatosis is known. After that, it is a simple process of therapeutic follow up that ensures resolution of the problem. As Malassezia folliculitis has a tendency to recur, treatment must be two-pronged. Therapy must be directed both at restraining yeast overgrowth as well as tackling predisposing factors, to avoid recurrence.

Specific treatment for Malassezia folliculitis can be divided into:

1) Topical treatment that includes;

• Antidandruff shampoo as a cleanser
• Topical antifungal agents, especially ketoconazole or ciclopirox creams or econazole foaming solution

2) Oral treatment

• Azole antifungal agents including ketoconazole, fluconazole and itraconazole can be used in the treatment of pityrosporum folliculitis. Despite its efficacy, oral ketoconazole has the potential for adverse effects, and oral Itraconazole is the preferred oral treatment option.

Pityrosporum folliculitis references

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