French Heartworm Mimics Myeloma? Rare Electrophoretic Pattern in Canine Angiostrongylosis

Unusual Electrophoretic Pattern in a Dog Infected With Angiostrongylus vasorum

Alice Kéfer, Hélène Machiels, Gaëlle Vincken, Clare Pitchford, Élodie Roels

Background

Angiostrongylus vasorum (French heartworm) is an emerging parasite in dogs, commonly causing respiratory and cardiovascular signs, and sometimes coagulopathies. Biochemical changes usually include mild hyperglobulinemia with polyclonal gammopathy, but atypical electrophoretic findings are rare. This case report describes, for the first time, a gammopathy pattern resembling a monoclonal or restricted polyclonal response in chronic angiostrongylosis.

Methods

A 7-year-old female pug with six months of cough and dyspnea was referred after a positive quantitative PCR for A. vasorum. Hematology, serum biochemistry, urinalysis, thoracic radiography, echocardiography, abdominal ultrasound, and Leishmania/FourDx testing were performed. Protein capillary zone electrophoresis (CZE) characterized the serum protein profile. Treatment included fenbendazole (10 days), imidacloprid/moxidectin spot-on (monthly), and tapering corticosteroids. Follow-up involved repeated imaging, lab testing, and bone marrow aspiration to exclude neoplasia or co-infections.

Results

Initial diagnostics revealed non-regenerative anemia, eosinophilia, basophilia, hyperproteinemia (109 g/L) due to hyperglobulinemia (81 g/L), and severe proteinuria (UPCR 7.54). CZE showed a restricted polyclonal (oligoclonal) beta peak and a tall, narrow gamma peak, initially concerning for monoclonal gammopathy. Thoracic imaging suggested chronic parasitic pneumonia. After therapy, clinical signs, hyperglobulinemia, and proteinuria resolved completely; electrophoretic tracing normalized; pulmonary changes improved radiographically. No infectious or neoplastic comorbidities were identified. Two years later, the dog remained clinically well apart from mild exercise intolerance and occasional seizures, unrelated to angiostrongylosis.

Limitations

The absence of immunofixation limited the ability to definitively distinguish between true monoclonal and restricted polyclonal gammopathy. As a single case, generalizability is limited. The splenic nodule noted on ultrasound likely represented a benign regenerative lesion but was not histologically confirmed.

Conclusions

Chronic A. vasorum infection can induce unusual electrophoretic changes mimicking monoclonal gammopathy, which typically signals hematologic malignancy. Recognition of this pattern is important to avoid misdiagnosis of neoplasia. Chronic parasitic infection should be considered among differentials when electrophoresis reveals narrow gamma peaks. Effective anthelmintic therapy can resolve both clinical and biochemical abnormalities.

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