Rhinosporidium seeberi

• Protozoan head and neck infection previously mistaken for a fungal infection

Background

Microbiology

• 18S rDNA sequencing has shown that Rhinosporidium seeberi is a protistan parasite
• Has never been cultured
• Forms round, thick-walled cysts (sporangia) in the submucosa, varying in diameter from 100 to 350 μm, often visible through the mucosa as white dots
• Mature cysts become filled with numerous spores (endospores), which on release become new cysts — kind of like Coccidioides

Epidemiology

• Occurs worldwide, with most cases in India and Sri Lanka

Clinical Manifestations

• Rhinosporidiosis is a chronic, usually painless localized pedunculated masses of the mucous membranes
• Lesions increase over months to years
• Most commonly affects the nose and nasopharynx, sometimes presenting with nasal obstruction or epistaxis
• Can also affect the eye or orbit, and rarely the skin as verrucous pedunculated lesions
• Rare cases involve the vagina, urethra, or penis
• Dissemination is rare

Diagnosis

• Presumably clinical suspicion with or without PCR or DNA sequencing
• With appropriate history, may be able to determine from biopsy
• Differential for spherules: Coccidioides, Rhinosporidium, Emmonsia

Management

• Surgery with electrocoagulation of the lesion base

Further Reading

• Pfaller MA and Diekema DJ. Unusual Fungal and Pseudofungal Infections of Humans. J Clin Microbiol. 2005;43:1495. doi: JCM.43.4.1495-1504.2005