A Rare case of Osteonecrosis of the jaw related to Imatinib
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A 72-year-old Caucasian male came complaining of submandibular and right laterocervical pain with onset several days earlier. Medical history revealed that the patient had CD117-positive GISTs with a c-Kit genetic mutation. He had been on imatinib at doses of 400 mg/day for 3 months followed by 600 mg/day for 4 months and then 800 mg/day.

Examination, initially conducted by an ENT specialist, showed slight swelling at the right mandibular angle, multiple laterocervical and right submandibular lymphadenopathies, and hot reddened skin without signs of fistulas. Oral examination showed exposed bone in the right retromolar triangle, halitosis and sialorrhea.

Medical history included surgical removal of the distal root of the first lower molar 10 years earlier. The dentist confirmed the mobility of the mandibular right first molar and anaesthesia/hypoesthesia of the right half of the lower lip, suggesting homolateral mandibular nerve compression. When the stitches were removed on day 7, the wound appeared to have healed. Five weeks after the extraction, the patient had pain in the same region and halitosis but did not seek medical advice, preferring to take NSAIDs and the antibiotic again (1 g amoxicillin and clavulanic acid, every 12 hours). Since the pain did not resolve, a week later he presented where ENT examination was carried out. The specialist ordered an X-ray of the dental arches which showed sequestration of the right mandibular bone involving the retromolar triangle.

An oral swab was taken and after disinfecting the oral cavity with 0.2% chlorexidine with anti-discoloration system, a bone fragment measuring 2.5×1.5 cm was removed together with underlying gingival tissue. The bone was sent to the pathology lab for examination. (CBCT) was requested. The patient was prescribed antibiotics (3 g/day amoxicillin and clavulanic acid and 500 mg/day levofloxacin) and discharged.

The pathology results available 72 hours later indicated positivity for Staphylococcus aureus, Candida albicans, Escherichia coli, and Enterococcus faecalis. Since the antibiogram showed sensitivity to levofloxacin, the patient continued the therapy already prescribed, to which fluconazole was added for C. albicans. CBCT showed a large area of osteonecrosis of the right hemimandibular body and angle with erosion of the vestibular cortex and complete destruction of the lingual cortex involving the mylohyoid line and the mandibular canal. Microscope examination of the tissues confirmed the clinical diagnosis of diffuse osteonecrosis and absence of neoplastic cells, therefore secondary localisations from GIST were excluded. Employing the Naranjo adverse drug reaction probability scale to determine the association of imatinib with osteonecrosis, the score revealed a probable adverse drug reaction.

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5410424/