INTRODUCTION
Rhinosporidiosis is a chronic granulomatous disease caused by Rhinosporidium seeberi. It most commonly affects the nose, nasopharynx, and conjunctiva. Extranasal sites of rhinosporidiosis like skin, subcutaneous, muscle, and bone are very rare.[1]
CASE REPORT
A 35-year-old male patient presented to the orthopedic department, with a painful swelling of size 4 × 3 cm in the proximal part of the right forearm for six months. On examination, there was a discharging sinus. No nasal mass was found. Excision and curettage were done, and samples were sent for histopathological examination to the Department of Pathology.
On gross examination, there were multiple bits of grey-white bone as well as soft tissue. The tissue was processed, and hematoxylin and eosin (H and E) staining was done.
Microsections show bony trabeculae and numerous sporangia in various stages of maturation. The sporangia contains endospores. The intervening stroma is fibrocollagenous, containing mixed inflammatory cells. So, a diagnosis of disseminated rhinosporidial osteomyelitis was established [Figure 1].
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Figure 1: Shows bony trabeculae and sporangia in various stages of maturation (H and E, 100×)
DISCUSSION
Rhinosporidiosis is now an emerging infectious disease caused by Rhinosporidium seeberi.[2] It is considered a parasitic protist of the eukaryotic group Mesomycetozoea.[3,4]
Rhinosporidium seeberi causes granulomatous inflammation at mucocutaneous sites like the nose, which is most frequently involved. Other sites like the conjunctiva, trachea, nasopharnyx, skin, bone, and genitourinary tract are less frequently involved.[5]
Infection most frequently occurs through the traumatized nasal epithelium in the natural aquatic habitat of R. seeberi.[6] Auto-innoculation and the hematogenous spread of rhinosporidiosis to other sites are seen.[6]
Histopathology shows sporangia in various stages of maturation. The sporangia are thick walled spherical structures that contain endospores. The stroma is fibromyxomatous, containing mixed inflammatory cells. Mature sporangia may rupture and release the endospores.
Rhinosporidium seeberi causes confusion with another microorganism, Coccidioides immitis.[6] This latter has similar mature stages represented by large, thick-walled, spherical structures containing endospores, but the spherules are smaller (diameter of 20–80 μm versus 50–1000 μm) and contain small endospores (diameter of 2–4 μm). Coccidiodes are negative for mucicarmine.[6]
Myospherulosis is also confused with rhinosporidiosis. The capsule of rhinosporidiosis is refractile, thick, double walled, and birefringent, which are absent in myospherulosis.[7]
CONCLUSION
Extranasal rhinosporidiosis is rare, and disseminated rhinosporidial osteomyelitis is also rare. Histopathology is the gold standard for the diagnosis of rhinosporidiosis. It can help in early diagnosis and differentiating the lesion from other benign lesions and malignant tumors.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
REFERENCES
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