Rhinosporidiosis is a chronic granulomatous disease caused by Rhinosporidium seeberi, mainly affecting the mucous membrane of nose, nasopharynx, and eyes. Involvement of bone though rare has been reported along with other mucocutaneous lesions. But bony involvement without any mucocutaneous lesion is very rare and only few cases are documented. Here we report a case of rhinosporidiosis of distal radius without any other lesion, which has not been reported in English language-peer reviewed literature, to the best of our knowledge.
Keywords: Extranasal rhinosporidiosis, radius, rhinosporidiosis
Rhinosporidiosis is known to be a chronic granulomatous lesion affecting nasal mucosa mainly, caused by a fungus Rhinosporidium seeberi. , Lesions of unusual sites (lachrymal sac, lip, palate, trachea, bronchi, parotid duct, vagina, vulva, urethra) are summarized by Karunaratne in his exhaustive monograph , and later on in other literatures ,, also. Though it has a global distribution, 90% cases are from Asia, mainly from south India, Sri Lanka, and Pakistan and less than 5% cases are from Africa and the Western countries.  However, majority of the cases were associated with mucocutaneous involvement of nose or nasal mucosa. , Here we present an unusual case of rhinosporidiosis affecting skin and bone mimicking bone tumor without any mucocuteneous lesion.
A 37-year-old male from poor socioeconomic status, farmer by occupation presented with complaint of a painless cauliflower-like growth measuring 15 × 17 cm over left forearm [Figure 1] near wrist joint for last 2 years. He noticed it when its size was about of a small marble, gradually it increased up to present size, but it never was associated with pain. For this he applied indigenous medicines without any good result. Two months before its surface eroded while taking bath, and bleeding stopped by some pressure at local hospital and it was referred to us at outpatient department (OPD). There was no other similar swelling over his body. He has no other significant past medical or surgical history or any similar illness in his family.
On examination, the swelling was firm in consistency, mobile on horizontal and restricted mobility on vertical direction, no major functional abnormality except mild restriction on extension of dorsum of hand. There was no palpable lymphnode in axilla, There was no nerve impairment in that limb. The ulcer over cauliflower-like mass bled easily on touch. He was normotensive. Clinical diagnosis was squamous cell carcinoma. Skiagram and computed tomography of the region showed involvement of bones-lower end radius and carpal bones [Figure 2]. Incisional biopsy showed necrotic areas with inflammatory cells without any evidence of malignancy.
He was normoglycemic with normal hemogram and normal renal biochemical parameters. Chest X-ray was normal. Serological tests for human immunodeficiency virus were negative. The large mass including lower end of left radius was excised, a fibular strut graft was harvested from contralateral fibula, graft was made upside down and implanted in the place of excised mass, and was arthrodesised with 3rd metacarpal with a 7 hole small dynamic compression plate and 3′5 mm 3 cortical screws each proximally and distally. Wrist was arthrodesised in maximum functional position that was slightly dorsiflexed and neutral rotation.
On histopathological examination it showed typical feature of rhinospodiosis with sporangia at different stages that involved the bone also [Figure 3].
He was doing well postoperatively, and was put on dapsone 100 mg daily for the next 6 months without any recurrence in 1 year follow up visit. However, due to arthrodesis, patient was having limited mobility on that wrist in functional position.
Rhinosporidiosis is a noncontagious chronic granulomatous condition commonly found in India and Sri-Lanka and rarely in the Western world.  The causative agent is R. seeberi, initially known as fungus, first discovered by Malbran (1892) and described by Seeber (1900).  Its exact taxonomic classification is still in debate. ,, Herr (1999) classified the organism as mesomycetozoa based on biological analysis of its ribosomal deoxyribonucleic acid.  Ahluwalia et al. demonstrated large cells and nanocytes of microcystis in round bodies of rhinosporidium by light and electron microscopy. , Recently Fredricks et al. , utilized 18s ribosomal DNA sequence to link R seeberi and classified it Dermocystidium genus: aquatic protistan fish parasites of the DRIPs (Dermocystidium, the Rosette agent, Ichthyophonus and Psorospermium) clade. DRIPs is a branch on evolutionary tree near the point of divergence of animals and fungi.
Most of the cases, the patients presented from the rural areas and poor socioeconomic strata  as in our case. Its mode of transmission is not clearly determined yet. Contaminated water, dust, and soil are the likely source of infection. ,, Some are of the opinion that trauma to the mucosa is an essential precondition for contamination. , In experimental animal, it is not possible to introduce the disease by inoculation and it is also not possible to culture the organism in vitro or in vivo. , There is no evidence of transmission of the disease from man to man or animal to man till now. ,,
Usually the lesion presents as a discrete, friable, painless slow-growing polypoidal pedunculated or sessile masses, which are richly vascular and bleeds on touch.  Nasal mucosa (70%) and conjunctiva is the most common site of infection, but other rare sites are larynx, maxillary antrum, skin of limbs, lachrymal sac, urethra, vagina, parotid duct, bone, and rectum. ,, Only seven cases have been reported till date in English literature mentioning rhinosporidiosis involving bone.  Among them only two cases showed exclusive bone involvement (earlier cases involvement was on talus and clavicle, respectively) without any mucocuteneous lesion.  Present case also shows exclusive bone involvement without any evidence of mucocuteneous involvement [Table 1].
Mode of spread may be either direct auto inoculation from mucosal rhinosporidiosis or hematogenous. ,, In cases of bone involvement three clinical settings can occur: (a) bone involvement with presence of mucocutaneous lesion as nasal polyp, (b) as a part of disseminated rhinosporidiosis, and (c) only primary bony lesion without any other organ involvement,  as in our case.
Histopathology is the only way to confirm the diagnosis. ,, It reveals chronic inflammatory cell infiltrate composed of plasma cells, lymphocytes along with foreign body giant cells surrounding characteristic sporangia, seen as globular cysts of various sizes at various stages of maturity lined by well-defined chitinous wall. ,, Inside the sporangia numerous endospore are present.
The disease is usually benign but only two fatal cases of disseminated rhinosporidiosis have been reported till date.  Surgical excision followed by electro cauterization of the base is the mainstay of management, ,, as done in our present case. Recurrence has also been reported due to inadequate excision. Sometimes curettage with excision of bone , or partial amputation of the limb , may be done when excision is not possible. Dapsone is the recommended antimicrobial agent to prevent recurrences in disseminated cases or when complete excision is not feasible. 
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[Figure 1], [Figure 2], [Figure 3]