Rhinosporidiosis

Rhinosporidiosis is a chronic granulomatous disease with polypoidal, pedunculated, friable, vascular mass, surface studded with yellow-white dots (strawberry-like). It involves most commonly mucosa, particularly nasal mucosa, and less frequently in skin and other organs.[1,2] This condition is caused by Rhinosporidium seeberi, which was earlier considered a fungus-like organism due to its morphological characteristics with endospores containing sporangium in the infected tissue.[1,3,4] Current molecular taxonomic evidence suggests this organism is a hydrophilic protistan parasite belongs to Mesomycetozoea, a clade known for its pathogenicity in certain fish and amphibians.[1,3,4] The disease is reported from most of the countries globally, with tropical and subtropical predominance. Majority of the cases and outbreaks are reported in endemic countries, especially Southeast Asian countries like India, Sri Lanka, as well as from South American regions, especially Argentina and Brazil.[2,4] Rhinosporidiosis manifests in four clinical forms: nasal, ocular, cutaneous, and disseminated forms. Usually, the condition is nonlethal, but mortality has been reported in cases with mucosal polypoidal mass obstructing the airways.[5,6] There is a lack of sufficient evidence related to the reservoir of the organism, mode of transmission, and pathogenesis. Although many of the studies linked the exposure to waterbodies during baths, there is evidence of traumatic inoculation of organisms as well as exposure to dry dust, dirt, and sand storms, especially in ocular cases with the possibility of airborne transmission.[2] The lesions involving genitourinary tracts suggest the possibility of sexual contact as a mode of transmission. Although the organism reported animal infections, particularly in cattle, horses, mules, and dogs, there is no evidence of zoonotic or man-to-man transmission.[7] In India, human cases are reported from Tamil Nadu, Pondicherry, Kerala, Andhra Pradesh, West Bengal, and Chhattisgarh. Certain regions, such as Raipur and Chhattisgarh, reported a large number of cases. India also documented animal infections in bullocks, cows, and captive swans.[7,8] As the Rhinosporidium seeberi is culture resistant, the diagnosis is primarily clinical, and further confirmation is based on microscopy, especially with histopathology or cytopathology with Hematoxylin and Eosin (H and E) stain, May–Grünwald–Giemsa stain and periodic acid–Schiff stain.[1,7] The potassium hydroxide (KOH) microscopy is also useful in diagnosis.[3] The morphological evidence with endospores containing sporangia is characteristic of R. seeberi. Organisms like Coccidioides immitis are usually differentiated from R. seeberi by the size of sporangia, endospores, and the number of spores, which are usually higher. Furthermore, the Mucicarmine stain will stain the R. seeberi sporangia and endospores better than the C. immitis.[3,4,7] There are no serological tests for this organism.[3] Radiological investigation may be helpful in identifying the mass lesions in deeper and cavitary regions. Although the 18S small subunit ribosomal DNA polymerase chain reaction (PCR) and sequencing are used in taxonomical and evolutionary investigation, there are no validated and standardized molecular investigations in routine diagnosis.[4] Surgical excision of the mass with electrocauterization of the polyp base is the mainstay of treatment. The recurrence following surgery is common in rhinosporidiosis.[2] Among various antimicrobial compounds such as diaminodiphenyl sulfone (SDD, i.e. dapsone), pentavalent antimony compounds like neostibasan and antifungal agents such as amphotericin are implicated in treatment, dapsone is the preferred drug and are suggested for treatment following surgical excision.[9] There are case reports documented clinical failure to dapsone therapy. There is a lack of sufficient evidence for drugs other than dapsone as there are documented spontaneous recovery or recovery following surgery without any antimicrobial compounds.[1] An observational cross-sectional study by Banjara et al., published in the Jan 2025–Jun 2025, issue of Tropical Parasitology, describes 104 cases in and around Raipur between March 2022 and January 2024.[10] Furthermore, the study emphasized various involvement anatomical sites, clinical presentation, risk factors, particularly the bathing practice among the rural and lower socioeconomic population, clinical diagnosis and pathological characterization of spongia and endospores of Rhinosporidium seeberi, and histopathological diagnosis. Furthermore, many of the high endemic areas in India particularly, the Raipur and surrounding area, documented a large number of cases over decades.[10] However, molecular surveillance and characterization of the organism from suspected clinical samples or histopathological examination confirmed clinical samples, paraffin tissue blocks of such cases, and the environment surrounding the patients’ residences are lacking. More studies are required for molecular genomic surveillance for the presence of R. seeberi in various environmental niches. The cultivation of this culture-resistant pathogen in artificial media is the main challenge for surveillance. More studies on various epithelial carcinoma cell lines for their potential to serve as cell lines are required.[11] Molecular methods focusing on 18S small subunit ribosomal DNA PCR sequencing or next-generation sequencing targeting the R. seeberi for extensive surveillance of various environments such as various waterbodies. The surveillance may be combined with ongoing surveillance targeting various pathogens in waterbodies as part of one health approach. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.