EXPRESS: Evaluation of the clinical course of immune-mediated polyneuropathy in cats following treatment with human intravenous immunoglobulins.

Human IVIg appears safe and effective in cats with IMPN, warranting consideration as a treatment option.

This retrospective case series evaluated the clinical outcomes of nine cats diagnosed with immune-mediated polyneuropathy (IMPN) treated with human intravenous immunoglobulins (hIVIg) across two veterinary referral hospitals between 2018 and 2025. IMPN is characterized by generalized lower motor neuron weakness with a remittent or relapsing clinical course, and evidence-based treatment guidelines for severely or chronically affected cats remain limited. Cats received hIVIg at 1–2 g/kg divided over 2–4 days (0.5 g/kg/day), and follow-up ranged from 8 to 51 months (median 17 months). Eight of nine cats demonstrated clinical improvement following hIVIg administration, achieving ambulatory status (>5 steps) within a median of 4 days. The median time to partial recovery was 14 days, and complete recovery was achieved at a median of 20 days. One non-responder subsequently improved with prednisolone therapy. Relapses occurred in four cats; however, relapse severity was reduced compared to initial presentation, and all affected cats recovered. The remaining five cats remained relapse-free throughout the follow-up period. No significant adverse effects were reported, suggesting hIVIg is well tolerated in cats. The study is limited by its small, retrospective, non-controlled design and absence of a comparison group. The authors conclude that hIVIg may be a viable treatment option for cats with both acute and chronic IMPN presentations, while emphasizing the need for larger prospective studies comparing hIVIg to corticosteroids or no treatment to firmly establish efficacy.

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