Pityrosporum Folliculitis: Itchy Rash on Back

A 34-year-old man is referred to the dermatology clinic for treatment of a persistent eruption on his chest and back. Previous treatments included oral doxycycline, minocycline, and ampicillin along with topical clindamycin solution. The patient notes that the lesions are occasionally itchy and infrequently drain pus. He is in good health, denies recreational drug use, and takes no oral prescription medications. Examination reveals multiple erythematous papules and scattered pustules on his trunk. His face is unaffected.

What is the most likely diagnosis?

1. Steatocystoma multiplex
2. Acne fulminans
3. Pityrosporum folliculitis
4. Methicillin-resistant Staphylococcus aureus (MRSA) folliculitis

Pityrosporum Folliculitis

Malassezia (Pityrosporum) folliculitis is an acneiform eruption initially described by Weary et al in 1969.¹ The disorder is caused by an overgrowth of Malassezia yeast strains (formerly known as Pityrosporum) normally present in skin flora.² Yeast overgrowth leads to follicular occlusion and disturbance of the skin microbiome. This triggers an inflammatory response that produces perifollicular erythema and pustule formation on seborrheic skin areas.³  

Malassezia folliculitis is common in adolescents and young adults. An increased incidence of infection has been reported in hot and humid climates and in those who have predisposing factors such as excessive sweating, immunosuppression, and systemic corticosteroid or broad-spectrum antibiotic use.  It presents as monomorphic papulopustular skin lesions on the trunk, upper arms, and face. Comedones are absent and itching may be intense.

Differential diagnoses include acne vulgaris, bacterial folliculitis, and eosinophilic folliculitis.⁴ Diagnostic studies such as microscopic evaluation, cultures, and biopsies can aid in the diagnosis. Microscopic evaluation reveals round and budding yeast cells predominantly in the upper and central portions of a dilated hair follicle.

The goal of therapy is to lower cutaneous yeast burden and establish a pre-infection commensal microbiome. The most effective treatment is an oral anti-yeast medication as the pathogen populates hair follicles beneath the surface.⁵ Topical agents are useful as adjunctive therapy as well as for maintenance and prophylaxis. To prevent recurrence, topical weekly therapy with ketoconazole shampoo is of benefit. Individuals with multiple risk factors may need monthly dosing with either fluconazole or itraconazole.

Alexandra Stroia, BS, is a medical student at the Lake Erie College of Osteopathic Medicine in Erie, Pennsylvania; Stephen Schleicher, MD, is director of the DermDox Dermatology Centers, associate professor of medicine at Geisinger Commonwealth Medical College, and clinical instructor of dermatology at Arcadia University and Kings College.

References

1. Weary PE, Russell CM, Butler HK, Hsu YT. Acneiform eruption resulting from antibiotic administration. Arch Dermatol. 1969;100:179-183.
2. Malgotra V, Singh H. Malassezia (Pityrosporum) folliculitis masquerading as recalcitrant acne. Cureus. 2021;13(2):e13534. doi:10.7759/cureus.13534
3. Rubenstein RM, Malerich SA. Malassezia (Pityrosporum) folliculitis. J Clin Aesthet Dermatol. 2014;7(3):37-41.
4. Cohen PR, Erickson C, Calame A. Malassezia (Pityrosporum) folliculitis incognito: Malessezia-associated folliculitis masked by topical corticosteroid therapy. Cureus. 2020;12(1):e6531. doi:10.7759/cureus.6531
5. Ayers K, Sweeney SM, Wiss K. Pityrosporum folliculitis: diagnosis and management in 6 female adolescents with acne vulgaris. Arch Pediatr Adolesc Med. 2005;159(1):64-67. doi:10.1001/archpedi.159.1.64

Originally published on Clinical Advisor.