Endocrine Abstracts

Case history: A 67-year-old-lady was first seen in the endocrinology clinic in December 2015 for management of her osteoporosis-deemed to be secondary to menopause with alcohol excess as an additive factor. This had been confirmed on the bone densitometry scan. She had previously been on Alendronate from July 2012 to April 2015, but discontinued this due to intolerance. Considering her latest bone mineral densitometry (BMD) values (in g/cm²) of 0.766 (T-score of -2.6) at the lumbar spine and 0.704 (T-score of -1.9) at the left hip, it was deemed that the best way forwards would be cutting down on alcohol, calcium and Vitamin-D supplementation and intravenous (IV) Zolendronate. She received the first dose of IV Zolendronate in January 2016, and received the 3rd dose of IV Zolendronate in February 2018. Her post-Zolendronate BMD values (in g/cm²) were 0.817 (T-score of -2.0) at the lumbar spine and 0.701 (T-score of -2.0). She had not reported any new fractures on this drug nor did she develop any complications secondary to the Zolendronate and hence she was kept on a drug-holiday with a plan to monitor her progress and BMD. The endocrinology team had last reviewed her in early December 2022. Around late December 2022, she started experiencing pain in the LR6 tooth, and underwent a dental extraction in January 2023. Following this, intense pain started developing at the site and hence she was referred to the maxillofacial team, who diagnosed her with Osteonecrosis of the jaw (ONJ), for which she required 3 months of Doxycycline.

Discussion: Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is defined as the exposure of the bone in the maxillofacial region for more than 8 weeks, in patients who are under bisphosphonate treatment without any radiation treatment, and who have undergone dental surgery including dental implant placement. For those receiving IV bisphosphonates, the incidence of BRONJ ranges from 5-20%. Amongst the bisphosphonates, Zolendronate is the most potent drug in causing BRONJ because of its high potency in slowing down bone turnover. The mean time for development of BRONJ after Zolendronate can be as long as 84 months, especially in those with underlying cancer. In our patient, the BRONJ developed 84 months after receiving the first dose of Zolendronate, with a long latent period of 59 months between the last dose and the development of BRONJ. To the best of our knowledge, this is the longest latent period reported.