Systematic review of anti-IL-5 biologics in hypereosinophilic syndrome kidney disease reports low certainty evidence.
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Key Takeaway
Consider that treatment efficacy conclusions are very low certainty and the 40% IgG4/IgG ratio remains unvalidated.
This publication is a systematic review with narrative synthesis examining the utility of anti-IL-5 and IL-5Rα biologics in patients with histologically confirmed hypereosinophilic syndrome-related kidney disease. The review analyzed 42 cases to characterize pathology findings and therapeutic evidence across the included literature.
Acute eosinophilic interstitial nephritis predominated at 54.8% (23/42), followed by thrombotic microangiopathy at 19.0% (8/42) and chronic interstitial fibrosis at 11.9% (5/42). Glomerular lesions occurred in 14.3% (6/42) of cases. IgG4-RKD-like features were observed in 21.4% (9 cases). Median IgG4+/IgG+ ratios were 21% (IQR 14-30%), remaining below 40%. Treatment response to anti-IL-5/IL-5Rα biologics showed 100% improvement (14/14) in all reported instances.
The authors note significant limitations, including uncontrolled study designs, high heterogeneity, and selection bias from biopsy requirements. Certainty ratings were low for descriptive pathology findings and very low for IgG4/IgG ratio observations and treatment efficacy conclusions. Publication bias and risk of bias further limit interpretation.
The 40% IgG4/IgG ratio remains unvalidated and should not be used diagnostically. International prospective registries and individual patient data meta-analyses are needed to establish evidence-based management. Clinicians should interpret these findings with caution given the very low certainty regarding treatment efficacy.
View Original Abstract ↓
BackgroundRenal involvement in hypereosinophilic syndrome (HES) occurs in 5-10% of patients but remains poorly characterized. Diagnostic overlap with IgG4-related kidney disease (IgG4-RKD) presents clinical challenges.ObjectiveTo characterize the clinicopathologic spectrum of histologically confirmed HES-related kidney disease, examine diagnostic differentiation from IgG4-RKD, and appraise therapeutic evidence.MethodsSystematic review with narrative synthesis following PROSPERO-registered protocol (CRD420261307200). Six databases were searched from inception to February 27, 2026. Dual independent screening and domain-specific GRADE assessment were performed. Due to uncontrolled study designs and high heterogeneity, narrative synthesis was conducted rather than quantitative meta-analysis.ResultsFrom 2, 247 records, 37 studies (42 cases) met inclusion criteria. Acute eosinophilic interstitial nephritis predominated (54.8%, 23/42), followed by thrombotic microangiopathy (19.0%, 8/42), chronic interstitial fibrosis (11.9%, 5/42), and glomerular lesions (14.3%, 6/42). Nine cases (21.4%) exhibited IgG4-RKD-like features with IgG4+/IgG+ ratios below 40% (median 21%, IQR 14-30%). However, substantial technical heterogeneity limits clinical applicability. Fourteen cases received anti-IL-5/IL-5Rα biologics; all reported improvement with no documented failures, suggesting publication bias. No randomized controlled trials exist for HES-related kidney disease.Certainty of evidenceDescriptive pathology findings were rated low certainty (downgraded for selection bias from biopsy requirement). IgG4/IgG ratio observations were very low certainty (downgraded for risk of bias, inconsistency, and indirectness). Treatment efficacy conclusions were very low certainty (downgraded for all GRADE domains, with publication bias and indirectness being most critical).ConclusionThis systematic review provides hypothesis-generating observations on HES-related kidney disease with low to very low certainty evidence. The 40% IgG4/IgG ratio remains unvalidated and should not be used diagnostically. International prospective registries and individual patient data meta-analyses are needed to establish evidence-based management. These findings require prospective validation before clinical application.
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