A TYPICAL PRIMARY EUMYCETOMA OF THE KNEE MIMICKING AN EPIDERMAL INCLUSION CYST: A RARE CASE REPORT

Abstract

Eumycetoma is a chronic granulomatous fungal infection of the skin and subcutaneous tissue that predominantly affects the foot following traumatic inoculation. Primary involvement of the knee is exceptionally uncommon and may present without the classical triad of painless swelling, multiple discharging sinuses, and extrusion of fungal grains, resulting in diagnostic uncertainty. Such atypical presentations can closely resemble benign soft tissue lesions, delaying definitive diagnosis and appropriate management. Primary eumycetoma involving the knee is exceedingly rare and poses a significant diagnostic challenge because of its nonspecific clinical presentation. The absence of characteristic sinus tracts and grain discharge may lead to misdiagnosis as benign cystic lesions, while cytological evaluation can be inconclusive due to failure to sample fungal grains. Histopathological examination with special fungal stains remains the gold standard for definitive diagnosis. Early recognition and complete surgical excision, combined with appropriate antifungal therapy, are essential to prevent disease progression, recurrence, and osteoarticular involvement. This case highlights the importance of considering eumycetoma in the differential diagnosis of chronic painless knee swellings in endemic regions, even in the absence of classical clinical features. Histopathological examination should be pursued when clinical and cytological findings are inconclusive, as early diagnosis facilitates timely treatment and favorable functional outcomes.