Extralymphatic Wuchereria bancrofti Presenting as an Isolated upper Arm Swelling: A Rare Case Report from a Non-Endemic Region of India

Abstract

Background: Wuchereria bancrofti is a major cause of lymphatic filariasis and typically involves the lymphatic system. Extralymphatic presentation is uncommon and may create diagnostic difficulty, particularly in regions where filariasis is not routinely suspected. Case Presentation: A 31-year-old male migrant worker from Uttar Pradesh presented with a gradually progressive swelling over the lateral aspect of the right upper arm for approximately five months. There was no history of trauma, fever, pain, weight loss, night sweats, previous similar lesions, or clinical features suggestive of chronic lymphatic filariasis. Examination revealed a firm, non-tender, immobile subcutaneous swelling measuring approximately 1 × 1.6 cm, with no regional lymphadenopathy. Routine haematological investigations showed marked eosinophilia, with an eosinophil count of 44%. Ultrasonography demonstrated multiple serpiginous echogenic motile structures within a localised fluid-containing cavity, producing the characteristic filarial dance sign. Surgical exploration and drainage yielded multiple thread-like worm structures and inflammatory fluid. Gross examination showed a slender whitish worm measuring approximately 80 mm with a wrinkled tail end. Microscopy demonstrated numerous sheathed microfilariae morphologically consistent with Wuchereria bancrofti. Molecular testing performed at a reference laboratory confirmed Wuchereria bancrofti. The patient was treated with diethylcarbamazine, ivermectin, and albendazole, with complete clinical resolution and no recurrence during follow-up. Conclusion: This case highlights an unusual extralymphatic presentation of Wuchereria bancrofti as an isolated upper-arm swelling. Careful epidemiological history-taking, imaging, microscopy, and molecular confirmation were important for diagnosis. Filariasis should be considered in unexplained soft-tissue swellings, especially in individuals from endemic areas.