IgG4-Related Disease

📋 Key Information Summary

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IgG4-related disease (IgG4-RD) is a systemic fibro-inflammatory condition characterised by tumefactive lesions, a dense lymphoplasmacytic infiltrate rich in IgG4-positive plasma cells, storiform fibrosis, and obliterative phlebitis.
Diagnosis requires clinicopathological correlation: serum IgG4 >1.35 g/L is supportive but can be normal in up to 30–40% of confirmed cases; histopathology remains the gold standard.
Histopathological triad: lymphoplasmacytic infiltrate, storiform (cartwheel) fibrosis, and obliterative phlebitis with an IgG4+/IgG+ plasma cell ratio >40% on immunostaining.
ACR/EULAR 2019 classification criteria require entry criterion, exclusion criteria, and weighted domains (clinical, serological, imaging, histopathological) yielding a score ≥20 for classification.
Type 1 autoimmune pancreatitis (AIP) is the most common pancreatic manifestation; imaging shows a diffusely enlarged "sausage-shaped" pancreas with peripancreatic capsule-rim sign.
IgG4-related sclerosing cholangitis mimics primary sclerosing cholangitis and cholangiocarcinoma; long-segment distal bile duct strictures with associated AIP favour IgG4-RD.
Glucocorticoids are first-line therapy: prednisolone 0.6 mg/kg/day induction (typically 30–40 mg), tapered over 3–6 months with planned maintenance for 3 years in Japan/Australia.
Steroid-sparing agents (azathioprine, mycophenolate mofetil, methotrexate) are used for relapse prevention or when glucocorticoid toxicity is a concern.
Rituximab (anti-CD20, 1000 mg IV ×2 doses fortnightly) is highly effective for refractory or relapsing disease and emerging as first-line in some protocols.
Multi-organ involvement is the rule: pancreas, biliary tree, salivary/lacrimal glands, retroperitoneum, kidneys, aorta, lungs, and orbits may all be affected simultaneously or metachronously.
Monitor treatment response with serial serum IgG4 levels (but note IgG4 may remain elevated despite clinical remission), repeat imaging at 4–8 weeks, and CRP/ESR.
Malignancy must be excluded before initiating immunosuppression; pancreatic cancer, cholangiocarcinoma, and lymphoma are key differential diagnoses.
Relapse rates are 30–50% after glucocorticoid cessation; maintenance immunosuppression or rituximab reduces recurrence.
Aboriginal and Torres Strait Islander peoples may have delayed diagnosis due to healthcare access barriers; increased vigilance is required in communities with high autoimmune disease prevalence.

Introduction & Australian Epidemiology

IgG4-related disease (IgG4-RD) is a recently recognised immune-mediated fibro-inflammatory condition that can affect nearly every organ system. Originally described in the context of autoimmune pancreatitis, it is now understood as a distinct multisystem entity unified by characteristic histopathological features and elevated tissue IgG4-positive plasma cells.

The disease predominantly affects middle-aged to elderly men (male-to-female ratio approximately 2–3:1), with peak incidence in the 6th–7th decade of life. In Australia, the estimated prevalence is 5–10 per 100,000 population, though this is likely an underestimate given diagnostic challenges and under-recognition.

⚠️

Diagnostic delay is common. The median time from symptom onset to diagnosis in Australian series is 12–24 months, partly due to the overlap with malignancy, PSC, and other fibro-inflammatory conditions. A high index of suspicion is required.

Key epidemiological points relevant to Australian practice:

Type 1 autoimmune pancreatitis accounts for the majority of IgG4-RD presentations to Australian gastroenterology and hepatopancreatobiliary (HPB) units.
Retroperitoneal fibrosis is increasingly recognised as an IgG4-RD manifestation; the Prince Charles Hospital and Austin Health retroperitoneal fibrosis registries document growing case numbers.
IgG4-RD may mimic malignancy in up to 50% of cases at initial presentation, leading to unnecessary surgical resections if tissue diagnosis is not pursued.
The Australian national pathology laboratories (including Sonic Healthcare, Laverty, and public hospital pathology) have standardised serum IgG4 immunoassay availability since 2015.

Diagnosis

IgG4-RD diagnosis requires integration of clinical features, serological markers, imaging findings, and histopathology. No single test is pathognomonic; a multidisciplinary approach involving rheumatology, gastroenterology, pathology, and radiology is essential.

Serum IgG4

Upper limit of normal: 1.35 g/L (may vary slightly between Australian laboratories; confirm local reference ranges).
Sensitivity: approximately 60–70%; therefore 30–40% of patients with confirmed IgG4-RD have normal serum IgG4.
Specificity: elevated IgG4 is not unique to IgG4-RD; levels may be raised in allergic conditions, infections, malignancy, and other autoimmune diseases.
Elevated IgG4 >2× ULN (i.e., >2.7 g/L) has higher specificity for IgG4-RD.
Serum IgG subclass analysis is available on request through major Australian referral laboratories (MBS item applicable).

Histopathology

Tissue diagnosis remains the gold standard. The characteristic histopathological triad includes:

Feature	Description	Diagnostic Value
Lymphoplasmacytic infiltrate	Dense infiltrate of mature lymphocytes and plasma cells, often with lymphoid follicle formation	High sensitivity; present in virtually all cases
Storiform fibrosis	Spindle-cell proliferation in a "cartwheel" or swirling pattern	Highly characteristic; distinguishes from other inflammatory conditions
Obliterative phlebitis	Inflammation and fibrosis obliterating venous lumina; arteries are typically spared	Most specific feature; identified in 50–80% of biopsies

Immunohistochemistry for IgG4-positive plasma cells:

Absolute count: ≥10 IgG4-positive plasma cells per high-power field (HPF) in most organs; ≥50/HPF for pancreatic tissue.
IgG4+/IgG+ ratio: >40% is strongly supportive of IgG4-RD.
Core needle biopsy or surgical excision biopsy is preferred; fine-needle aspiration is generally insufficient for histopathological assessment.

ℹ️

Availability in Australia: IgG4 immunohistochemistry is available at all major tertiary hospital pathology departments and through specialist pathology providers. Request explicitly on the pathology form; turnaround time is typically 5–10 working days.

ACR/EULAR 2019 Classification Criteria

The 2019 ACR/EULAR classification criteria for IgG4-RD provide a standardised framework for research and clinical classification:

Entry criterion: At least one characteristic organ swelling/mass or organ dysfunction suggestive of IgG4-RD.
Exclusion criteria: 32 items excluding mimicking conditions (e.g., malignancy, infections, other autoimmune diseases).
Weighted inclusion criteria across four domains:

Domain	Item	Score
Clinical	Symmetric lacrimal, parotid, or submandibular gland enlargement	+3
	Pancreas involvement (diffuse enlargement/rim/hypoenhancement)	+4
	Biliary tract involvement	+3
Serological	IgG4 > ULN but ≤2× ULN	+4
Serological	IgG4 > 2× ULN	+6
Imaging	Multiorgan involvement on imaging	+2 to +5
Histopathological	Lymphoplasmacytic infiltrate + storiform fibrosis	+7
Histopathological	IgG4+/IgG+ >40% and ≥10 IgG4+ cells/HPF	+6

Classification threshold: Total score ≥20 after exclusion criteria are met.

HISORt Criteria for Autoimmune Pancreatitis

The HISORt criteria (Histology, Imaging, Serology, Other organ involvement, Response to therapy) remain widely used in Australian HPB centres for Type 1 AIP diagnosis:

H — Histology: Lymphoplasmacytic sclerosing pancreatitis on core biopsy or resection specimen.
I — Imaging: Characteristic pancreas imaging (diffuse enlargement, delayed enhancement, capsule rim, or focal mass).
S — Serology: Elevated serum IgG4 (>1.35 g/L) or other IgG subclass abnormalities.
O — Other organ involvement: Biliary strictures, salivary gland enlargement, retroperitoneal fibrosis, renal lesions, etc.
Rt — Response to therapy: Resolution or marked improvement with glucocorticoid trial (supports but does not establish diagnosis).

Diagnosis is established if any one group of criteria is fulfilled; combination of multiple groups strengthens diagnostic confidence.

GI & Hepatopancreatobiliary Manifestations

The gastrointestinal tract and hepatopancreatobiliary (HPB) system are the most commonly affected domains in IgG4-RD, accounting for approximately 60–70% of presentations in Australian tertiary centres.

Type 1 Autoimmune Pancreatitis (AIP)

Type 1 AIP is the pancreatic manifestation of IgG4-RD and the most common organ-specific presentation. It must be distinguished from Type 2 AIP (idiopathic duct-centric pancreatitis), which is not associated with IgG4 elevation or systemic involvement.

Feature	Type 1 AIP (IgG4-related)	Type 2 AIP
Age	60–70 years	40–50 years
Sex ratio	M:F = 3:1	M:F = 1:1
Serum IgG4	Elevated in 60–70%	Normal
Systemic involvement	Common (biliary, salivary, retroperitoneal)	Absent
Relapse rate	30–50%	<10%
IBD association	Rare	Up to 30%

Characteristic imaging findings (CT/MRI):

Diffuse enlargement: "Sausage-shaped" pancreas with loss of normal lobular contour.
Capsule-rim sign: Hypoenhancing rim of tissue surrounding the pancreas on portal venous phase CT; represents peripancreatic fibrosis/inflammation.
Delayed enhancement: On dynamic CT or MRI, the pancreatic parenchyma shows delayed enhancement relative to normal pancreas.
Focal mass form: May mimic pancreatic adenocarcinoma; absence of upstream duct dilatation, vascular encasement, or distant metastases favours AIP.
MRCP: Long-segment distal CBD stricture with upstream biliary dilatation; pancreatic duct may be attenuated or irregular.

🚨

Critical: Pancreatic cancer must be rigorously excluded before diagnosing AIP. Features that favour malignancy include: rapid weight loss, obstructive jaundice without fluctuation, vascular invasion, distant metastases, and lack of response to a 2–4-week corticosteroid trial. Endoscopic ultrasound (EUS) with fine-needle biopsy (FNB) is essential when doubt remains.

IgG4-Related Sclerosing Cholangitis (IgG4-SC)

IgG4-SC is the biliary manifestation of IgG4-RD and is present in approximately 60–90% of patients with Type 1 AIP. It is critical to distinguish IgG4-SC from primary sclerosing cholangitis (PSC) and cholangiocarcinoma, as treatment approaches differ fundamentally.

Feature	IgG4-SC	PSC	Cholangiocarcinoma
Age at diagnosis	60–70 years	30–40 years	>60 years
Sex	Male predominance	Male predominance	Male predominance
Stricture pattern	Long-segment distal CBD; proximal intrahepatic uncommon	Multifocal, beaded intrahepatic	Focal, irregular, asymmetric
IgG4 level	Elevated	Usually normal	Occasionally elevated
Concurrent AIP	Present in ~80%	Absent	Absent
Response to steroids	Excellent	Minimal	None
Malignancy risk	Low	Cholangiocarcinoma risk 10–15%	IS the malignancy

Retroperitoneal Fibrosis

IgG4-RD accounts for approximately 50–60% of idiopathic retroperitoneal fibrosis cases.
Presents as a peri-aortic soft-tissue mass (typically below the renal arteries) encasing the ureters and causing obstructive uropathy.
MRI is preferred over CT for monitoring soft-tissue response; FDG-PET/CT may be used to assess disease activity.
Bilateral ureteric stenting or nephrostomy may be necessary for acute obstructive renal failure prior to immunosuppression.

Sclerosing Sialadenitis & Other Head/Neck Involvement

Küttner tumour: Chronic sclerosing sialadenitis of the submandibular gland presenting as a firm, painless mass mimicking malignancy.
Mikulicz disease: Bilateral symmetrical enlargement of lacrimal, parotid, and submandibular glands — now recognised as IgG4-RD (distinct from Sjögren syndrome).
Orbital involvement: Proptosis, restrictive strabismus, infraorbital nerve enlargement.
Tissue biopsy is essential to exclude lymphoma and Sjögren syndrome.

Multi-Organ Involvement

IgG4-RD is inherently a multi-organ disease. In Australian series, approximately 40–60% of patients have involvement of two or more organs at diagnosis. Recognised sites include:

Organ System	Manifestation	Key Investigation
Pancreas	Type 1 AIP	CT/MRI, EUS-FNB
Biliary tree	IgG4-SC	MRCP, ERCP with brushings
Retroperitoneum	Retroperitoneal fibrosis	CT/MRI abdomen-pelvis
Salivary/lacrimal glands	Sclerosing sialadenitis, Mikulicz	Ultrasound, biopsy
Kidneys	Tubulointerstitial nephritis, mass lesions	CT, renal biopsy
Aorta/periaortic tissue	Inflammatory aortic aneurysm, periaortitis	CT angiography, FDG-PET
Lungs	Nodules, bronchovascular thickening, pleural thickening	HRCT, VATS biopsy
Orbits	Orbital pseudotumour, dacryoadenitis	MRI orbits, biopsy
Meninges	Hypertrophic pachymeningitis	MRI brain with contrast
Thyroid	Riedel thyroiditis	Thyroid biopsy

Investigations

A systematic investigative approach is essential for diagnosis, exclusion of mimics, and baseline assessment prior to treatment.

Available

Serum IgG subclasses (including IgG4)

MBS item available. Standard immunoassay through major Australian pathology networks. IgG4 >1.35 g/L is elevated; >2× ULN more specific. Can be normal in 30–40% of cases.

Available

Liver function tests, CRP, ESR

Elevated ALP and GGT in IgG4-SC. CRP/ESR may be mildly elevated. Routine MBS items.

Available

CA 19-9, CEA

To exclude pancreatic/biliary malignancy. CA 19-9 may be mildly elevated in AIP with biliary obstruction but typically <100 U/mL. MBS item available.

Available

CT abdomen/pelvis with IV contrast (pancreatic protocol)

MBS item. First-line imaging for pancreatic and retroperitoneal assessment. Pancreatic protocol includes arterial and portal venous phases.

Available

MRCP / MRI abdomen with MRCP

MBS item. Superior for biliary ductal assessment, differentiating IgG4-SC from PSC and cholangiocarcinoma. Avoids radiation.

Specialist

Endoscopic ultrasound (EUS) with FNB

MBS item (restricted to specialist settings). Essential for tissue diagnosis and malignancy exclusion. Core biopsy with 19G needle preferred for histopathological assessment. Available at major tertiary centres (e.g., RPAH, Austin, RBWH).

Specialist

ERCP with biliary brushings/biopsy

MBS item. For IgG4-SC assessment and cholangiocarcinoma exclusion. Therapeutic biliary stenting if obstructive jaundice present.

Specialist

FDG-PET/CT

MBS item (limited indications). Useful for assessing extent of multi-organ disease and differentiating active inflammation from fibrosis. Available at public PET centres and through request to NPS.

Available

IgG4 immunohistochemistry on tissue biopsy

Available at all major hospital pathology departments and specialist pathology networks. Must be specifically requested. Includes IgG4 and IgG stains with plasma cell counting.

Specialist

Flow cytometry of tissue/blood

To exclude B-cell lymphoma, which may mimic IgG4-RD. Available through haematology referral centres.

Treatment

Treatment of IgG4-RD aims to achieve remission of active inflammation, prevent organ damage from fibrosis, and manage relapses. Most patients respond dramatically to glucocorticoids, but relapse rates are significant and long-term immunosuppression strategies are often necessary.

⚠️

Before starting immunosuppression: Ensure malignancy has been adequately excluded with appropriate tissue sampling (EUS-FNB, surgical biopsy). Starting corticosteroids before histological confirmation may mask or delay cancer diagnosis.

First-Line: Glucocorticoid Induction

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Prednisolone

Panafcortelone® · Generic · Glucocorticoid

Adult dose 0.6 mg/kg/day PO (typically 30–40 mg/day), maintained for 2–4 weeks, then tapered by 5 mg every 1–2 weeks to 20 mg/day, then 2.5 mg every 2–4 weeks. Total induction period 3–6 months.

Paediatric dose Limited data; 0.5–1 mg/kg/day with specialist supervision

Route Oral

Duration 3–6 months (induction); may require maintenance at 5–7.5 mg/day for 3 years

Renal adjustment Not required; monitor fluid retention and electrolytes

Hepatic adjustment Not required; monitor in severe hepatic impairment

PBS status ✔ PBS General Benefit

Expected response: Most patients show symptomatic and serological improvement within 2–4 weeks. Imaging response (reduction in organ swelling, resolution of capsule rim) is seen at 4–8 weeks. Prednisolone should be continued at the initial dose for 2–4 weeks before commencing taper.

Maintenance strategy (Australian approach): Following successful induction, many Australian centres maintain low-dose prednisolone (2.5–5 mg/day) for 1–3 years, particularly in patients with multi-organ involvement or elevated IgG4 at baseline. The Japanese consensus recommends 3-year maintenance; Australian practice varies.

Steroid-Sparing Agents

Steroid-sparing agents are indicated for: (1) relapse prevention, (2) steroid-dependent disease, (3) steroid intolerance/contraindications, and (4) as adjuncts to rituximab in refractory disease.

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Azathioprine

Imuran® · Generic · Thiopurine immunosuppressant

Adult dose 2–2.5 mg/kg/day PO (typically 100–150 mg/day). Check TPMT/NUDT15 genotype before commencing.

Key monitoring FBC fortnightly × 4–6 weeks, then monthly × 3 months, then 3-monthly. LFTs monthly initially. TPMT/NUDT15 genotyping before initiation (PBS-funded).

PBS status ✔ PBS General Benefit

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Mycophenolate mofetil

CellCept® · Generic · Inosine monophosphate dehydrogenase inhibitor

Adult dose 1 g PO BD (2 g/day total). Alternative when azathioprine is contraindicated or not tolerated.

Key monitoring FBC and LFTs monthly × 3 months, then 3-monthly

Renal adjustment Dose reduce in eGFR <25 mL/min; avoid in severe renal impairment

PBS status ⚠ PBS Restricted Benefit — authority required for approved indications

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Methotrexate

Methoblastin® · Generic · Antifolate immunosuppressant

Adult dose 15–25 mg PO/SC once weekly with folic acid 5 mg weekly (not on MTX day)

Key monitoring FBC, LFTs, creatinine every 2 weeks × 6 weeks, then monthly

Renal adjustment Dose reduce or avoid if eGFR <30 mL/min

PBS status ✔ PBS General Benefit

Second-Line / Refractory Disease: Rituximab

Rituximab (anti-CD20 monoclonal antibody) is increasingly used in IgG4-RD for relapsing, refractory, or steroid-intolerant disease. Depletion of B-cells addresses the central immunopathogenic mechanism and produces rapid, often dramatic, responses.

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Rituximab

MabThera® · Riximyo® · Anti-CD20 monoclonal antibody

Adult dose 1000 mg IV on Day 1 and Day 15 (induction). Repeat cycles every 6 months if relapse occurs, or fixed schedule every 6 months for maintenance.

Paediatric dose 375 mg/m² IV weekly × 4 doses (per lymphoma protocol); limited IgG4-RD paediatric data

Route Intravenous infusion (with premedication: paracetamol, antihistamine, methylprednisolone 100 mg IV)

Key monitoring Check HBV status (HBsAg, anti-HBc) before initiation. Monitor serum IgG, IgA, IgM pre-treatment and periodically. CD19/CD20 B-cell counts to confirm depletion. Screen for hypogammaglobulinaemia if repeated cycles.

PBS status ✘ Authority Required — PBS-listed for RA, ANCA vasculitis, lymphoma; IgG4-RD use may require Authority application or compassionate access

✅

Rituximab efficacy: In published case series and the RIgG4-RD trial, rituximab achieves clinical response rates of 85–95% in IgG4-RD. It is particularly effective for orbital, salivary gland, retroperitoneal, and pancreatic disease. Discuss PBS authority pathway with your local pharmacy or apply via Special Access Scheme (SAS) Category B if not PBS-eligible for IgG4-RD indication.

Treatment Algorithm

1

Diagnosis & Exclusion of Malignancy

Tissue biopsy with IgG4 immunohistochemistry. Exclude malignancy with appropriate imaging and tumour markers. Baseline serum IgG4.

2

Induction: Glucocorticoids

Prednisolone 0.6 mg/kg/day (30–40 mg) for 2–4 weeks, then taper over 3–6 months. Assess response clinically, serologically (IgG4), and with imaging at 4–8 weeks.

3

Maintenance or Steroid-Sparing

Consider azathioprine, mycophenolate, or methotrexate for relapse prevention, especially with multi-organ disease, elevated IgG4 at baseline, or steroid intolerance. Low-dose prednisolone (2.5–5 mg) maintenance for up to 3 years.

4

Relapse or Refractory Disease

Re-induction with glucocorticoids if mild/limited relapse. Rituximab 1 g IV × 2 doses fortnightly for significant relapse, steroid-refractory disease, or steroid contraindications. Consider repeat rituximab every 6 months for maintenance.

5

Long-Term Monitoring

Serum IgG4 every 3–6 months. Imaging (CT or MRI) 3–6 monthly for first 2 years, then annually. Monitor for organ damage from fibrosis (e.g., biliary strictures, ureteric obstruction). Screen for diabetes mellitus if AIP present.

Monitoring Response

Clinical: Symptom resolution (jaundice, gland swelling, mass-related symptoms) within 2–4 weeks of glucocorticoid initiation.
Serological: Serum IgG4 typically falls within 4–8 weeks. However, IgG4 may remain elevated despite clinical remission in 30–50% of patients (so-called "serological non-responders"). Do not escalate therapy based on IgG4 alone if the patient is clinically well.
Imaging: Repeat CT or MRI at 4–8 weeks post-induction. Reduction in organ swelling, resolution of capsule-rim sign, and improvement in biliary strictures are expected. Complete normalisation may take months.
Biomarkers: CRP, ESR, and liver function tests (in IgG4-SC) provide complementary monitoring data.
Relapse definition: Recurrence of symptoms, new organ involvement, or reappearance of imaging abnormalities after initial response. Fluctuation in IgG4 alone is not diagnostic of relapse.

Special Populations

🤰 Pregnancy

Prednisolone

Considered safe in pregnancy at lowest effective dose. Category A (oral corticosteroids). Avoid high doses in first trimester if possible; benefits usually outweigh risks in active IgG4-RD.

Azathioprine

Compatible in pregnancy (Category D but widely used in IBD/transplant). TPMT status should be confirmed. Continue at stable dose.

Methotrexate

Contraindicated — Category X. Teratogenic. Must be ceased ≥3 months before conception (both sexes). Reliable contraception essential.

Mycophenolate mofetil

Contraindicated — Category D. Teratogenic. Cease ≥6 weeks before conception. Switch to azathioprine for pregnancy planning.

Rituximab

Category C. Avoid in pregnancy if possible. B-cell depletion may persist in neonate for months. Use only if life-threatening disease and no alternatives.

👶 Paediatric

Incidence

IgG4-RD is very rare in children (<1% of cases). Limited paediatric-specific data. Management guided by adult evidence with specialist input from paediatric rheumatology or gastroenterology.

Dosing

Glucocorticoids: 0.5–1 mg/kg/day prednisolone. Azathioprine: weight-based dosing with TPMT testing. Rituximab: 375 mg/m² × 4 weekly doses (off-label). Refer to tertiary paediatric centre.

👴 Elderly

Glucocorticoid risks

Increased risk of steroid-induced diabetes, osteoporosis, adrenal suppression, and infections. Use bone protection (calcium, vitamin D, consider bisphosphonate). Monitor glucose. Aim for steroid-sparing agents early.

Immunosuppression

Higher infection risk with combination immunosuppression. Consider age-adjusted screening (zoster vaccination before rituximab, pneumococcal vaccination).

🫘 Renal Impairment

IgG4-related TIN

IgG4-related tubulointerstitial nephritis may cause renal impairment directly. Treatment with glucocorticoids often improves renal function. Monitor closely.

Drug adjustments

Mycophenolate: dose reduce if eGFR <25. Methotrexate: avoid or dose reduce if eGFR <30. Azathioprine: use standard dosing but monitor FBC closely. Rituximab: no renal adjustment required.

🫁 Hepatic Impairment

Consideration

IgG4-SC may cause secondary biliary cirrhosis if untreated. Azathioprine is hepatotoxic — monitor LFTs closely. Methotrexate is hepatotoxic — avoid in significant liver disease. Glucocorticoids may be preferred first-line in hepatic impairment.

🛡️ Immunocompromised

Infection screening

Screen for latent TB (IGRA), hepatitis B (HBsAg, anti-HBc), hepatitis C, HIV, and Strongyloides (if ATSI or tropical exposure) before immunosuppression. Rituximab may cause prolonged hypogammaglobulinaemia — monitor IgG levels.

Vaccination

Complete all vaccinations ≥4 weeks before rituximab. Live vaccines contraindicated during immunosuppression. Annual influenza and COVID-19 vaccination recommended.

Aboriginal and Torres Strait Islander Health Considerations

Aboriginal and Torres Strait Islander Health

Diagnostic delay

Aboriginal and Torres Strait Islander peoples experience longer delays to specialist referral and diagnosis for rare immune-mediated diseases. IgG4-RD may be underdiagnosed due to limited access to specialist pathology (IgG4 immunohistochemistry), imaging, and tertiary gastroenterology/rheumatology services in regional and remote Australia.

Remote access

Specialist availability for EUS, ERCP, and advanced imaging is concentrated in metropolitan and major regional centres. Patients in remote Northern Territory, Far North Queensland, and Western Australia may require interstate transfer for diagnostic procedures. Telehealth for rheumatology and gastroenterology follow-up is available through MBS-funded specialist telehealth items.

Autoimmune disease prevalence

Aboriginal and Torres Strait Islander peoples have higher rates of certain autoimmune conditions (e.g., Type 1 diabetes, autoimmune hepatitis). While IgG4-RD prevalence in this population is not well characterised, the higher baseline autoimmune burden may predispose to IgG4-RD. Increased clinical awareness is needed.

Comorbidity burden

Higher rates of diabetes, chronic kidney disease, and cardiovascular disease may complicate glucocorticoid therapy. Steroid-induced diabetes and fluid retention are particularly relevant. Engage Aboriginal Health Workers and primary care teams in comorbidity management and medication monitoring.

Medication access

PBS prescriptions can be dispensed through Aboriginal Community Controlled Health Services (ACCHS). Closer to My Health (Closing the Gap) PBS co-payment measure reduces out-of-pocket costs for PBS medicines. Ensure patients are registered for Closing the Gap PBS co-payment to minimise medication cost barriers.

Culturally safe care

Engage Aboriginal Health Workers, Aboriginal Liaison Officers, and cultural support services in the care team. Acknowledge kinship and community obligations. Provide information in plain language and through trusted community health services. Use the Australian Indigenous HealthInfoNet and RHDAustralia resources for culturally appropriate health information.

RHDAustralia alignment

While RHDAustralia primarily focuses on rheumatic heart disease, their models of remote specialist outreach, patient recall systems, and chronic disease management are directly applicable to managing IgG4-RD in remote communities. Consider liaison with local RHDAustralia coordinator for chronic disease follow-up frameworks.

📚 References

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3. Okazaki K, Kawa S, Kamisawa T, et al. Amendment of the Japanese Consensus Guidelines for Autoimmune Pancreatitis, 2013-I. Concept and diagnosis of autoimmune pancreatitis. J Gastroenterol. 2014;49(4):567–588.
4. Khosroshahi A, Wallace ZS, Crowe JL, et al. International consensus guidance statement on the treatment of IgG4-related disease. Arthritis Rheumatol. 2015;67(7):1688–1699.
5. Kamisawa T, Zen Y, Pillai S, Stone JH. IgG4-related disease. Lancet. 2015;385(9976):1460–1471.
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7. Carruthers MN, Topazian MD, Khosroshahi A, et al. Rituximab for IgG4-related disease: a prospective, open-label trial. Ann Rheum Dis. 2015;74(6):1171–1177.
8. Detlefsen S, Klöppel G. IgG4-related disease: with emphasis on the histopathological diagnosis. Stem Cell Investig. 2017;4:88.
9. Matsubayashi H, Uesaka K, Sugiura T, et al. IgG4-related sclerosing cholangitis and autoimmune pancreatitis. Hepatobiliary Surg Nutr. 2020;9(5):616–630.
10. Stone JH, Brito-Zerón P, Bosch X, Ramos-Casals M. Diagnostic approach to the complexity of IgG4-related disease. Mayo Clin Proc. 2015;90(7):927–939.
11. Australian Institute of Health and Welfare (AIHW). Aboriginal and Torres Strait Islander health performance framework. Canberra: AIHW; 2023.
12. Australian Commission on Safety and Quality in Health Care (ACSQHC). National Safety and Quality Health Service Standards. 2nd ed. Sydney: ACSQHC; 2021.
13. Wallace ZS, Zhang Y, Perugino CA, et al. Clinical phenotypes of IgG4-related disease: an analysis of two international cross-sectional cohorts. Ann Rheum Dis. 2019;78(3):406–412.
14. Culver EL, Sadler R, Simpson D, et al. Elevated serum IgG4 levels in diagnosis, treatment response, organ involvement, and relapse in a prospective IgG4-related disease UK cohort. Am J Gastroenterol. 2017;112(4):733–743.
15. Royal Australasian College of Physicians (RACP). Clinical guidelines for the management of autoimmune conditions in Australia. Sydney: RACP; 2022.