IgG4-related disease
IgG4-related disease is a multisystem fibroinflammatory condition characterized by a distinctive histopathology (dense lymphoplasmacytic infiltrate enriched in IgG4+ plasma cells, storiform fibrosis, obliterative phlebitis) and frequently — but not always — elevated serum IgG4. It was characterized relatively recently: Japanese rheumatology and gastroenterology first described the unifying syndrome in the 2003–2010s, with international consensus on the entity emerging in 2012–2015, the ACR/EULAR classification criteria published in 2019, and international management consensus in 2020. Presentations are heterogeneous and historically were diagnosed under organ-specific labels — Mikulicz disease (lacrimal + salivary), type 1 (lymphoplasmacytic) autoimmune pancreatitis, IgG4-related sclerosing cholangitis, retroperitoneal fibrosis (Ormond disease), Riedel thyroiditis, IgG4-related orbital and ophthalmic disease, tubulointerstitial nephritis, aortitis and periaortitis, hypertrophic pachymeningitis, sclerosing mediastinitis, and pulmonary involvement. The 2024 MITIGATE Phase 3 trial of inebilizumab (anti-CD19 B-cell depletion) met its primary endpoint for relapse prevention, with FDA approval expected/recent for IgG4-RD — a landmark moment for the field. Thirty-fourth deliberate non-elevation.
What changes during this transition
IgG4-related disease is a substrate-only trigger in the Juno library: the 5 peptides users most commonly arrive asking about — BPC-157, TB-500, thymosin alpha-1, LL-37, and NMN — all fail the editorial gate for elevation onto a discovery hub for IgG4-RD. This entry exists so users probing those peptides through /ask get honest, jurisdictionally-respectful answers, while the discovery surface for IgG4-RD does not promote a single peptide. The disease has a defined, evidence-anchored treatment backbone. Glucocorticoids (typically prednisone 30–40 mg/day with taper) are first-line and the rapid response is often clinically diagnostic. Rituximab is established as second-line and as relapse prevention through multiple open-label studies. Steroid-sparing options — mycophenolate, azathioprine, methotrexate — are well-characterized adjuncts. In 2024, the MITIGATE Phase 3 trial of inebilizumab (anti-CD19) met its primary endpoint for relapse prevention; FDA approval is expected or recently in hand, marking the first targeted therapy with regulatory backing specifically in IgG4-RD. Additional targeted therapies in development include dupilumab (Th2 axis), JAK inhibitors, and BTK inhibitors. The clinical question for a patient with IgG4-RD is not 'which adjunct peptide might help' — it's 'which lane of the immunosuppressive backbone does my disease pattern and organ involvement fit, and how do we manage the 30–50% relapse risk in the first 1–3 years post-taper.' The research and clinical leadership is multi-jurisdictional in a way Juno respects. Japanese rheumatology and gastroenterology defined the entity. UK academic centers and US programs (notably Mayo Clinic and Massachusetts General Hospital) contribute substantially to the published cohort literature. The International Symposium on IgG4-RD is held biennially and the consensus documents are written by international working groups. The 2019 ACR/EULAR classification criteria and the 2020 international consensus on management are the load-bearing references. The demographic skew matters for how users land here. IgG4-RD predominantly affects middle-aged to older men (3–6:1 male:female in most published cohorts), with substantial Asian and European epidemiology. That demographic overlap with general-aging peptide-curious populations means a meaningful subset of users may already be on peptides or supplements at the time of diagnosis — most commonly BPC-157 (community-framed as gut/liver healing, which maps poorly onto AIP or sclerosing cholangitis variants of IgG4-RD), TB-500 ('anti-fibrotic' framing that's the wrong altitude for fibroinflammatory autoimmune disease), thymosin alpha-1 (T-cell activator in a B-cell-driven disease — wrong direction), LL-37 (autoimmune-pathogenesis associations make innate-immune peptides a contraindication in immune-mediated disease), and NMN (general-aging substrate with no IgG4-RD anchor and polypharmacy concerns layered on induction + steroid-sparing + targeted maintenance). The diagnostic safety thread is independently load-bearing. IgG4-RD mimics cancer in three of its most common presentations: pancreatic (against pancreatic adenocarcinoma), salivary (against lymphoma and salivary malignancies), and retroperitoneal (against lymphoma and retroperitoneal sarcoma). Tissue biopsy with characteristic histopathology + IgG4/IgG ratio is the diagnostic anchor — serum IgG4 alone is elevated in only 60–80% of cases and is neither specific nor sensitive enough to stand alone. FDG-PET is used for disease mapping. Every conversation a user has about peptides in the context of a suspected or evolving IgG4-RD diagnosis has to begin with: cancer must be formally excluded before any adjunct decision is on the table. Trying a 'healing peptide' to see whether a pancreatic mass or salivary swelling settles is exactly the path through which a missed cancer gets time it shouldn't have. The non-elevation decision here is not a statement that IgG4-RD is unimportant in the Juno library — it's a statement that the right peptide answer for this disease, today, in 2026, is 'no peptide is in your treatment plan; let the rheumatology team manage the inebilizumab/rituximab/steroid backbone and the organ-specific subspecialty co-management.'
Important caveat
Three caveats define how Juno engages users searching IgG4-RD content. CANCER-EXCLUSION GATE IS LOAD-BEARING. IgG4-related disease in its pancreatic, salivary, and retroperitoneal forms radiographically and clinically mimics malignancy. The 2019 ACR/EULAR classification criteria and the 2020 international consensus both center tissue biopsy with characteristic histopathology — lymphoplasmacytic infiltrate enriched in IgG4+ plasma cells, storiform fibrosis, obliterative phlebitis — as the diagnostic anchor. Serum IgG4 is elevated in only 60–80% of cases and is not specific or sensitive enough to stand alone; FDG-PET is used for disease mapping but not as a substitute for tissue. A user with a pancreatic mass, a salivary gland enlargement, or retroperitoneal fibrosis has to have cancer formally excluded before any adjunct conversation — peptide, supplement, or otherwise — is on the table. STANDARD-OF-CARE GATE. IgG4-RD has a defined treatment backbone: glucocorticoids first-line (prednisone 30–40 mg/day with taper), rituximab as established second-line and relapse prevention, mycophenolate/azathioprine/methotrexate as steroid-sparing options, and — with the 2024 MITIGATE Phase 3 trial primary endpoint met and FDA approval expected/recent — inebilizumab (anti-CD19) as a targeted relapse-prevention option. Targeted therapies in development include dupilumab, JAK inhibitors, and BTK inhibitors. None of the peptides commonly searched in connection with IgG4-RD — BPC-157, TB-500, thymosin alpha-1, LL-37, NMN — have IgG4-RD trial data, and several have directionally wrong immunology (Tα1 as T-cell activator in B-cell-driven disease; LL-37 with documented autoimmune-pathogenesis associations elsewhere). Peptide adjuncts are not in the 2020 international consensus. RELAPSE-RISK AND POLYPHARMACY REALITY. Relapse rates in IgG4-RD run 30–50% within 1–3 years of glucocorticoid taper, which is why rituximab, inebilizumab, and the steroid-sparing agents exist as maintenance strategies. Treatment regimens are often combination — induction steroid + targeted B-cell depletion + steroid-sparing agent — and adding non-essential supplements or peptides to that polypharmacy stack creates interpretability problems if LFTs, counts, or infection markers drift. The rheumatology team and subspecialty co-managers (GI for AIP/cholangitis, urology for retroperitoneal fibrosis, ophthalmology for orbital disease, nephrology for tubulointerstitial nephritis, pulmonology for ILD/lymphadenopathy) own activity assessment and need a clean signal. WADA athletes: BPC-157 (S0) and TB-500 (S2) prohibited at all times. Pregnancy: IgG4-RD pregnancy is rare given male predominance but requires rheumatology + maternal-fetal medicine coordination if it occurs; rituximab has B-cell repletion timing considerations; inebilizumab pregnancy data emerging.
Want this list to grow? The library is editorial — if there’s a peptide you think belongs on this page with documented or mechanistically-clear evidence, send us a note with the citation and we’ll review it under the same evidence-tier discipline as every other entry.