Osteonecrosis of the external auditory canal in two patients on denosumab therapy

Medication-related osteonecrosis of the jaw (MRONJ) is a rare but well-recognized complication of treatment with anti-resorptive agents. Medication-related osteonecrosis of the external auditory canal (MROEAC), on the other hand, is even rarer and mostly reported during bisphosphonate exposure. Its pathophysiology is thought to involve complex multifactorial processes including inhibition of bone remodelling, altered angiogenesis, infection and inflammation. Due to the poor recognition of MROEAC, ear canal health is not routinely discussed with patients, and there is no requirement for auditory canal assessment prior to anti-resorptive therapy. We present 2 cases of denosumab associated MROEAC: a 72-year-old woman with osteoporosis treated with denosumab for 5 years (Case A), and an 84-year-old man with osteoporosis treated with denosumab for 6 years (Case B), both of whom presented with unilateral ear itch, and were subsequently diagnosed with MROEAC. Both patients were managed conservatively with topical corticosteroid, antimicrobial, antifungal ointment, and cessation of denosumab with subsequent elevation of bone turnover markers. In Case A, a course of teriparatide immediately after denosumab cessation did not improve bone erosion. Teriparatide was ceased due to patient’s concern with renal calculi, high bone resorption marker and vertebral fracture. A trial of risedronate was commenced with reduction of bone markers and epithelization of the auditory canal. In Case B, risedronate was commenced with reduction of bone markers and early healing of auditory canal at 4 months. Osteonecrosis of sites other than the jaw should be considered as a potential rare complication and balanced against the bone protection benefits of long-term anti-resorptive therapy. The optimal treatment strategy for MROAEC remains uncertain, currently there is no recommendation for routine auditory canal assessment prior to or during anti-resorptive treatment, but sequencing off established denosumab use with follow-on treatment to mitigate potential rapid bone loss needs to be considered.