Complex disposition of an enigmatic pathogen: rare electron microscopic manifestations in nasal rhinosporidiosis

Rhinosporidiosis is a polypoidal disease of the nose and mucocutaneous tissues, the diagnosis of which is based on the presence of round bodies believed to be causative agents of the disease. Historically, the round body has been considered to be a sporangium of a fungus Rhinosporidium seeberi but without any convincing evidence. Round bodies contain numerous daughter cells, which are likely in the infective stage and are shed through a rupture in the wall of the round body. The released single-celled organisms eventually develop into round bodies on availability of suitable transformative trigger and favourable environment. Surgical excision of the polyp by electrocautery is the only effective treatment; however, recurrence may occur due to spillage of infective endospores in the surrounding mucosa during removal. There are many enigmatic features of the causative agent of this disease, which have been baffling researchers for more than a century. Here we present some rare electron microscopic and previously unreported features of the coat of the round body and single-celled organism in nasal rhinosporidiosis.