Discussion
This case report documents a case of nasal rhinosporidiosis in a
paediatric patient at a Zonal Referral Hospital in Central Tanzania and
so far the first documented case in Central Tanzania and the
16th case countrywide. The disease has been reported
from about 70 countries with diverse geographical
features.7 The infrequently, isolated cases are
reported in other parts of the world and are mainly due to
migration.2,9
The disease is more common in younger age groups from the available
literatures and being more common in men than women with male to female
ratio being 4:12,10,11 These observations appear
similar to what has been observed in our case report where the affected
patient was an 11-year old male child.
Rhinosporidiosis and its causative organism Rhinosporidium seeberi have
been known for over a hundred years and it’s a rare infective chronic
granulomatous disease that remains to be endemic in some part of Asia
(India), although sporadic cases have been reported in America, Europe
and Africa4,5,15-17
To date the causative organism has never been isolated in vitro, and its
taxonomic position is unclear.19
In contrast with more recent fungal infections, some aspects of the
taxonomy, morphology, ontogenesis and epidemiology of those caused by
Rhinosporidium seeberi remain controversial and have not been resolved.
Though now related to a group of fish parasites referred to as the DRIP
clade, most pathologists and microbiologists initially considered it to
be fungus on the basis of its property to be stained by fungal stains
such as Gomori methenamine silver (GMS) and periodic acid-Schiff
(PAS).20,21
Available literatures indicated that a combination of host specificities
and resistance of Rhinosporidium to grow in culture may account for the
failure to produce experimental rhinosporidiosis.21Some authors proposed the class of Rhinosporidium seeberi to be
Mesomycetozoa.13,20,21. Fluorescent
in-situ-hybridization techniques provide evidence that the natural
habitat for Rhinosporidium seeberi are water reservoirs and perhaps soil
contaminated by waste. In addition, other aquatic microorganisms might
be relevant to a possible synergistic action in the establishment of
natural rhinosporidiosis.21
The class Mesomycetozoa has two orders, which are the Dermocystida and
the Ichthyophonida. In the order Dermocystida is the family
Rhinosporideaceae that includes Rhinosporidium seeberi, Dermocystidium
spp. and the rosette agent.21
The route of transmission for Rhinosporidium remains to be unclear even
though the presumed mode of infection from the natural aquatic habitat
of Rhinosporidium seeberi is through a traumatized epithelium commonly
called trans epithelial infection and this is most common in nasal
sites. For Rhinosporidium seeberi, various modes of spread have
been documented including; auto-inoculation through spillage of
endospores from polyps after trauma or surgery, haematogenous spread to
distant sites, lymphatic spread, and sexual
transmission.3,21 Rhinosporidiosis is prevalent in
rural settings, particularly among people working or in contact with
contaminated soil, stagnant water (ponds, or lakes) or
sand.21 In our case report, the patient gave a history
of contact with contaminated pond water and was residing in a rural
area. Similarly, the patient reported a history of contact with
feces of infected livestock and used to work in contaminated
agricultural fields. Such risk factors have been reported in the
available literatures.20,21
Interestingly about the incidence of the rhinosporidiosis is that while
several hundred people bathe in stagnant waters, only a few develop a
progressive pattern of the disease. This might indicate the existence of
predisposing factors in the host where the possibility of nonspecific
immune reactivity in the host, blood group and HLA types has been
suggested as important in the pathogenesis of Rhinosporidium seeberi in
the establishment of an initial focus of
infection.20,21
Since rhinosporidiosis has a slow course, lesions may be present for
many years before the patients become
symptomatic7,20,21 and this appears similar to what
was seen in our patient who reported a history of nasal obstruction and
intermittent epistaxis for 2 years.
Rhinosporidiosis manifests as tumor-like masses, usually of the nasal
mucosa or ocular, conjunctivae of humans and animals and patients with
nasal involvement often have masses leading to nasal obstruction or
bleeding due to polyp formation and it can spread to the nasopharynx,
oropharynx, and the maxillary antrum.1,3,20,21 The
patient reported in our case had an isolated friable mass localized in
the nasal cavity with no involvement of other anatomical sites such as
maxillary sinus. The diagnosis is established by observing the
characteristic appearance of the organism in tissue biopsies and
computerized tomography (CT) scans. The lesion is friable, vascular
pedunculated or sessile polyp, with a surface studded with tiny white
dots due to spores beneath the epithelium, giving a ‘ strawberry-like ’
appearance. The lesion in our case report was friable evidenced by nasal
bleeding upon probing.20
Systemic disease is rare but can include multiple mucocutaneous,
hepatic, renal, pulmonary, splenic or bone lesions associated with
fever, wasting, and even death.20,21
Though rare, spontaneous regression of Rhinosporidial growths has been
noted in animals and in humans and therefore, medical and/or surgical
intervention is necessary.20,21 Wide local surgical
excision of the Rhinosporidial growth is the treatment of choice to
reduce the risk of recurrence, though this may be associated with
significant morbidity due to hemorrhage and nasal septal
perforation.5,17 Therefore limited surgical excision
and adjuvant medical therapies, including antifungals such as
griseofluvin and amphotericin B, trimethoprim-sulphadiazine, and sodium
stibogluconate have been tried with varied success. All drugs were
endospore-static rather than endosporicidal. The strains obtained from
human and animal rhinosporidiosis have shown genetic variations that
might explain the variation of responses to some drugs though data on
antimicrobial drug resistance in Rhinosporidium seeberi is
lacking.20,21 The only drug appearing to have clinical
promise is Dapsone since it arrests the maturation of sporangia and
promotes fibrosis in the stroma when used as an adjunct to
surgery.22 It could therefore be expected that
pre-surgical Dapsone would minimize both hemorrhage by promotion of
fibrosis as well as preventing the colonization and infection of new
sites after the release of endospores from the surgically traumatized
polyps.23,24 Laser excision promises to be the
mainstream treatment of sinonasal rhinosporidiosis in the
future.25 Our patient was kept on dapsone for 6-months
after endoscopic nasal mass excision with no recurrence noted after
6-months of follow up. Our patient had complete nasal mass excision with
wide surgical margins and cautery of the base of the Rhinosporidial
growth endoscopically and was treated subsequently with Dapsone for
6-months.