A lesion of the patella: An unexpected location of Rosai-Dorfman disease: A case report

INTRODUCTION: Primary osseous Rosai-Dorfman disease (RDD) is a rare and benign disease that can pose diagnosis challenges. PRESENTATION OF THE CASE: We report the case of a 29-year-old woman who presented with pain in her left patellar region for the past 6 months with no other clinical sign especially no lymphadenopathy associated. A surgical excision was done. Histopathology confirmed the diagnosis of a primary RDD patellar disease. The patient was followed up for 2 months without any recurrence. The aim of this study was to present a rare case of RDD in a patellar location and to review clinicopathological features, therapeutic modalities, evolutionary aspects and prognosis of a primary patellar RDD. DISCUSSION AND CONCLUSION: The diagnosis of a primary osseous RDD without associated lymphadenopathy should be kept in mind when a sclero-lytic lesion is found. Excision of the lesion is the gold standard of the treatment.