# Medication-related osteonecrosis of the jaws: a series of 22 cases highlighting their histopathological features

## TL;DR

This study examines 22 cases of medication-related jaw bone death, focusing on its microscopic features and infection patterns.

## Contribution

The study reveals new histopathological features of MRONJ, including lamellar bone structure and high prevalence of Actinomyces infection.

## Key findings

- MRONJ predominantly affects the mandible in older African-Brazilian women.
- Osteomyelitis was present in 82% of cases, with Actinomycosis in 36.4%.
- MRONJ features include lamellar bone, osteon-like structures, and absence of osteoclasts.

## Abstract

This study aimed to assess the clinicopathological characteristics of medication-related osteonecrosis of the jaw (MRONJ), addressing histopathological features and bone structure. Twenty-two MRONJ patients were retrospectively evaluated for osteonecrosis, osteomyelitis, bacterial colonization, bone resorption, reactive bone, osteon-like structure, lamellar bone, and basophilic lines. Specific staining and fluorescence and polarized light microscopy assessments were also performed. The mandible was significantly more affected by MRONJ. There was a predominance of African-Brazilian women aged sixty and older. Osteomyelitis was present in 82% of patients. Actinomycosis was observed in 36.4% of MRONJ patients. Osteoclasts were absent in MRONJ but bone resorption was often seen. Basophilic lines were observed in more than 80% of the patients. The MRONJ patients exhibited lamellar bone with osteon-like structures. This study provided important insight into MRONJ, demonstrating a diverse histopathological spectrum and infection with Actinomyces and fungi. The condition was characterized by a necrotized lamellar bone structure and more frequently affected the mandible of older women.