Knee eumycetoma in Cameroon: diagnostic challenges and therapeutic management of a rare localization – a case report

Introduction: Mycetoma is a chronic, destructive infectious disease affecting the skin, subcutaneous tissues, and bone. It is caused by filamentous fungi (eumycetoma) or actinomycetes (actinomycetoma) and is characterized by grain formation. Although endemic in tropical and subtropical regions known as the “mycetoma belt,” Cameroon is not included in this area, which may contribute to diagnostic delays in non-endemic settings. Presentation of case: We report the case of a 50-year-old man from Cameroon presenting with a chronic fistulizing knee swelling associated with black-grain discharge, evolving over more than 1 year. Despite investigations, the diagnosis remained challenging. Clinical and paraclinical findings confirmed eumycetoma. The patient underwent marginal excision followed by split-thickness skin grafting and received adjuvant itraconazole therapy. At 36 months of follow-up, no recurrence was observed, and clinical outcomes were satisfactory. Discussion: Knee involvement in eumycetoma is rare and may mimic soft tissue tumors, leading to diagnostic delays, especially in non-endemic settings. Although typically associated with rural exposure in tropical regions, mycetoma should not be excluded based solely on atypical epidemiological features. Fistulization with black grains remains a key diagnostic clue, while imaging may be misleading, and histopathological confirmation is essential. Management relies on surgical excision with adequate margins, often requiring reconstructive procedures, combined with prolonged antifungal therapy and long-term follow-up due to recurrence risk. Conclusion: This case highlights the occurrence of mycetoma in non-endemic regions and underscores the importance of early recognition to reduce diagnostic delay and improve outcomes. Increased awareness among clinicians is essential to ensure timely diagnosis and appropriate management.