The ERIN (Evaluation of Rheumatologic Immune-related Adverse Events) registry—the first national, practice-based platform for tracking rheumatic irAEs in routine care—has begun shedding light on the complexity and treatment patterns of rheumatic complications associated with immune checkpoint inhibitor (ICI) therapy.

“Immune checkpoint inhibitors (ICIs) are a mainstay of cancer immunotherapy,” the authors noted. “However, their increasing use has led to more immune-related adverse events (irAEs), including rheumatic irAEs (rh-irAEs).”

Launched in May 2024 at LMU University Hospital, ERIN is a multicenter, clinician-facing registry open to adult patients with suspected or confirmed rh-irAEs during or after ICI therapy. Data collection includes rheumatologic and oncologic diagnoses, treatment details, and outcomes. As of May 2025, 9 German centers had contributed data for 40 patients. Results were reported at ACR Convergence and in Arthritis & Rheumatology.

Among enrolled patients (median age 65 years; 58% male), melanoma was the most common underlying malignancy (45%). Nivolumab and pembrolizumab were the leading ICIs used. The most frequent rh-irAE was RA-like polyarthritis (52.5%), followed by SpA-like syndromes (peripheral 15.0%, axial 9.1%) and PMR-like presentations (12.5%). Notably, axial SpA-like cases occurred in younger patients (median age 46), suggesting potential immune-age phenotype differences.

Severity varied: 55% of rh-irAEs were grade II, and 35% were grade III. ICIs were interrupted in 17.5% and permanently discontinued in 27.5% of cases. Systemic corticosteroids were used in 80%, while DMARDs—most commonly conventional synthetic agents—were used in patients who reached remission.

“RA-like polyarthritis was the most common rh-irAE, while axSpA-like manifestations occurred more often in younger patients, suggesting age-related immune patterns,” the authors wrote. “Systemic CS were initiated in most cases, underlining their key role in early management.”

“ERIN provides real-world insight into rh-irAEs under ICIs," concluded the study authors. "These findings emphasize rh-irAE heterogeneity and the need for personalized care.”

Gailis D, Ullrich F, Dombret S, et al. The ERIN Registry: real-world data on rheumatic immune-related adverse events from immune checkpoint inhibitor therapy [abstract]. Arthritis Rheumatol. 2025; 77 (suppl 9). https://acrabstracts.org/abstract/the-erin-registry-real-world-data-on-rheumatic-immune-related-adverse-events-from-immune-checkpoint-inhibitor-therapy/. Accessed October 17, 2025.