Case Report: Subcutaneous Dirofilariasis in a Lithuanian Patient

Introduction Dirofilaria repens is a mosquito-borne filarial parasite, mainly affecting carnivorous animals but can also cause zoonosis in humans as incidental hosts leading to ocular or subcutaneous dirofilariasis [1]. This case highlights the rarity of subcutaneous dirofilariasis with only seven cases reported in Lithuania for non-travelers [1,2]. Case Presentation A 64-year-old woman presented with a firm, mobile nodule on her right thigh, following an insect bite two months prior. After the bite, she experienced painful erythematous patches that spread bilaterally but without systemic symptoms. She had no history of traveling abroad. Her medical history includes atopic dermatitis. On examination, a firm, mobile 0,6 x 0,5 cm nodule on the right thigh was observed. Laboratory findings revealed no eosinophilia or elevated total IgE levels. Borrelia burgdorferi IgM/IgG antibodies test was negative. Stool examinatiom for helminth eggs and larvae was negative. Ultrasound revealed a well-defined 0,6 x 0,4 cm subcutaneous hypoechogenic lesion with multiple internal thin worm-like structures. The nodule and capsule were excised under local anesthesia and histopathological examination confirmed D. repens. Following the procedure, the patient experienced complete resolution of symptoms. Discussion Subcutaneous dirofilariasis typically presents as a painless, solitary, erythematous nodule with mild swelling [1]. Lithuania has recently been identified as an endemic region for D. repens, reflecting its growing prevalence [2]. The diagnosis relies on ultrasonography, histopathology and polymerase chain reaction, as serology lacks specificity. Pharmacotherapy is not recommended, and surgery remains the treatment of choice [1,3]. Conclusions This case highlights the increasing prevalence of Dirofilaria repens in Lithuania and raises awareness about the importance of considering dirofilariasis in patients presenting with subcutaneous nodules at any body site.