Rare metastatic alveolar echinococcosis of the chest-wall mimicking IgG4-related disease: diagnosis and treatment of the first reported case in Henan Province, China

Alveolar echinococcosis (AE), caused by Echinococcus multilocularis , is a life-threatening zoonosis primarily distributed in western China. This report describes the complete process of diagnosis, treatment, and etiological investigation of the first reported AE case in Henan Province. The patient presented with a rare AE metastasis to the chest-wall, involving the sternum and ribs, without any clear epidemiological association with AE-endemic areas. A 66-year-old female from southern Henan presented with a progressively enlarging, painful right anterior chest-wall mass. Imaging, histopathology, and serology (elevated IgG4, 90 IgG4 + plasma cells/hpf) prompted initial consideration of IgG4-related disease (IgG4-RD). Prednisone therapy failed, and the lesion rapidly progressed, eroding the sternum and ribs and extending into the anterior mediastinum. Metagenomic next-generation sequencing of purulent aspirate detected 50,632 reads (99.99% relative abundance) of E. multilocularis , confirming chest-wall AE. Radical resection was precluded by extensive involvement; treatment with oral albendazole (400 mg/day) was initiated. After two years, the lesion shrank from > 60 mm to 17 mm, with near-complete symptomatic resolution. Mitochondrial cox1 gene analysis placed the isolate within the Asian mitochondrial lineage of E. multilocularis , consistent with sequences reported from western China; the source of infection could not be definitively identified. This case highlights the diagnostic challenges of AE in non-endemic regions, including its ability to mimic IgG4-RD, and the critical role of mNGS in pathogen identification. Given the prolonged latency, high pathogenicity and sporadic occurrence of AE, heightened clinical awareness of E. multilocularis infection and long-term follow-up of patients with AE are urgently needed. Not applicable.