Rhinolithiasis was first described by Thomas Bartholin, Danish physician, in the 17th century (1 , 2 , 5 ). Since then, hundreds of cases have been reported in the literature (5 ). The rhinolithiasis incidence reported in the literature has been relatively rare; about 1 in 10,000 otorhinolaryngology patients. The usual age range for diagnosis of rhinolithiasis is between 8-25 years old with female predominance (2 , 5 ). The pathogenesis of rhinolithiasis is not clear (2 ). Rhinoliths originate from the deposition of magnesium, iron, calcium and phosphorus around a nidus, which can be endogenous or exogenous (1 , 2 ). The exogenous nuclei that are more prevalent include significantly different foreign bodies, placed in the nasal cavity generally during childhood. Children are interested in exploring their bodies and thus more prone to lodging foreign bodies in their nasal cavities or ear canals. Nasal foreign bodies can also be seen in adults, particularly those with mental retardation or psychiatric illness. The presence of foreign body leads to a local inflammatory reaction. Salts and minerals deposit around the core subsequently. The endogenous nuclei include intranasal thick secretions, epithelial debris, blood clots, bone fractures of visceral skull, and ectopic teeth (1 , 2 ). A screw was the nidus of rhinolithiasis in this case report. The patient did not have any psychiatric problem and therefore he had probably inserted the foreign body in his nasal cavity when he was younger.
The first chemical analysis of rhinolith was performed by Axmann in 1829. The main materials (up to 90%) are inorganic, such as calcium phosphate, calcium carbonate and magnesium phosphate, as well as other rare substances. The organic components may be derived from nasal secretion and lacrimal fluid (2 ).
Rhinoliths are generally seen in the floor of nose, about halfway between the anterior and posterior portions of the nasal cavity (5 ). In the literature review, some believe that rhinoliths are situated in the anterior half of the nares. Small rhinoliths are generally asymptomatic. Larger rhinoliths can lead to unilateral nasal discharge, nasal pain, swelling, sinusitis, or remain asymptomatic (1 , 2 , 5 ).
Erosions of the septum, maxillary sinus, and perforations have also been mentioned in the literature (5 ). They present as greyish irregular masses and feel hard, bony and gritty on probing (5 ). In many patients, the diagnosis accidentally follows other radiological examinations. The most important differential diagnoses of rhinolith include tori, impacted teeth, mycolith, odontoma, granulomatous diseases (syphilis and tuberculosis), osteoma, enchondroma, calcified polyps, haemangioma, dermoid, nasal polyp with osseous metaplasia, osteosarcoma, and chondrosarcoma (2 , 5 , 6 ). The complications reported are rhinosinusitis, septal and palatal perforations, recurrent otitis media, and dacryocystitis (2 ).
The radiological manifestations of rhinolith were first described by Maclntyre in 1900 (5 ). The typical radiological features of rhinolith are radio-opacity with central translucency. On CT scan, it presents as a homogenous, high density lesion with smooth mineralization. The central portion of the lesion may contain organic materials with probably a lower density or a foreign body (2 , 5 ). CT scan of paranasal sinuses can precisely determine the site and size of rhinolith and recognize any coexisting sinus disease which will probably require treatment (4 ).
Rhinoliths may be asymptomatic for many years until the continuous growth of rhinolith cause nasal obstruction, and maybe frequently misdiagnosed as rhinosinusitis, as our case. Although a number of cases have been reported, rhinolithiasis remains a relatively rare clinical entity and misdiagnosis can happen because of the failure to detect rhinolith in the anterior rhinoscopy. Rigid nasal endoscopy plays an important role in making a diagnosis and evaluating the posterior extent of a rhinolith without being exposed to radiation (2 ).
In the majority of cases rhinolith can be removed endoscopic ally, except for rare cases that will require extended surgical approaches such as lateral rhinotomy for complete removal of the stone (2 ). Surgeons can utilize lithotripsy to disintegrate the rhinoliths that cannot be removed surgically (4 ).
The main challenging aspect of this disease is misdiagnosis with more common diseases such as rhinosinusitis. Our case was a unique one in regard to an incorrect diagnosis twice by specialists because of vague history and an incomplete physical examination. The current case report stresses the importance of considering the possibility of rhinolithiasis in unilateral nasal obstruction and nasal discharge to prevent misdiagnosis and delayed diagnosis.
In conclusion, the diagnosis can be made by keeping a strong suspicion based upon symptoms, history of putting foreign body into the nose, physical examination, and complementary tests. The examination should include anterior rhinoscopy and rigid nasal endoscopy (1 ). Radiological assessments including simple X-ray and paranasal CT scan support the diagnosis by showing calcified concentrations in the nasal cavity and would be a great help in planning surgical approaches (1 ).
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