Unravelling <i>Nocardia</i>-induced Actinomycetoma from Central Maharashtra: Clinical Insights and Diagnostic Challenges

Introduction: Actinomycetoma is a chronic infectious granulomatous disease affecting the skin and subcutaneous tissue, caused by aerobic filamentous bacteria. Actinomycetoma due to Nocardia (Gram-positive, filamentous, acid-fast bacilli) is endemic in Africa, Mexico, and South and Central America. There are only a few cases reported in the literature from Maharashtra, specifically in Mumbai, Pune, and the Vidarbha region. Nocardial actinomycetoma around the knee is a rare presentation. Herein, we report a case of a 62-year-old male agricultural worker from the central Maharashtra region. Case Presentation: A 62-year-old agricultural worker presented with multiple discharging sinuses and swelling around the right knee without granules. Discharge from multiple sinuses was subjected to microbiological investigations [10% KOH mount, Gram stain, Ziehl-Neelsen (ZN) stain]. The KOH mount was negative, while the Gram stain revealed Gram-positive filamentous bacilli. Modified ZN stain demonstrated partially acid-fast filamentous bacilli, confirming Nocardia species. Histopathological examination revealed actinomycotic colonies surrounded by epithelioid cell granulomas. Imaging showed multiple hypoechoic interconnecting tracts on local ultrasound with the characteristic ‘dot-in-circle’ sign on contrast-enhanced MRI (knee). The final diagnosis was confirmed as actinomycetoma (caused by Nocardia) based on microbiological, histopathological, and radiological investigations. He was treated with a Modified Welsch regimen (injection amikacin 15 mg/kg/day intravenously (IV) in two divided doses with oral trimethoprim-sulphamethoxazole 35 mg/kg/day and oral rifampicin 10 mg/kg/day). Injection amikacin for 21 days constituted one cycle. Two such cycles were administered at an interval of 15 days. Oral co-trimoxazole and rifampicin were given daily without interruption. The size of the lesions and discharge reduced after a single cycle of amikacin. After the second cycle, all lesions dried up, with a few lesions showing healing with post-inflammatory hyperpigmentation. The patient was lost to follow-up after the completion of two cycles of therapy. Conclusions: Nocardial actinomycetoma poses a diagnostic challenge. Although Nocardia is a rare pathogen, it deserves consideration in the etiological differential diagnosis of mycetoma. Astute clinical examination with prompt laboratory evaluation can facilitate an accurate diagnosis. Early identification and timely initiation of effective therapy are crucial for achieving a favorable outcome and preventing complications.