IgG4-related disease — Rapid | Doctor’s Passport

Synopsis

Recognise the organ patterns of IgG4-related disease, distinguish inflammatory enlargement from cancer and infection, obtain architecture-preserving tissue with expert pathology, and prevent irreversible pancreatic, biliary, renal, orbital, neural and retroperitoneal fibrosis.

IgG4-related disease is a relapsing fibroinflammatory condition that forms tumefactive lesions in pancreas, bile ducts, salivary and lacrimal glands, orbit, kidneys, retroperitoneum, aorta, lung, meninges and pituitary.
Serum IgG4 supports but does not diagnose disease: mild elevation occurs in allergy, infection and malignancy, and a meaningful minority of biopsy-proven patients have a normal concentration.
First diagnostic priority is to exclude cancer and infection before corticosteroid, especially with a focal pancreatic or biliary mass, destructive lesion, atypical nodes or constitutional decline.
Reference tissue assessment uses organ architecture plus dense lymphoplasmacytic inflammation, storiform fibrosis and obliterative phlebitis, with IgG4-positive cell count and ratio interpreted by an expert organ pathologist.
The 2019 ACR/EULAR criteria classify research cohorts and should not be used as a stand-alone diagnostic or treatment threshold in an individual patient.
Map organs systematically: pancreas and bile ducts, salivary and lacrimal glands, orbit, chest, kidneys and urine, retroperitoneum and hydronephrosis, aorta, nodes and neuroendocrine symptoms.
Drain cholangitis or obstructed kidneys and protect optic, neural or vascular structures before expecting immunosuppression to reverse the mechanical emergency.
First-line induction for active organ-threatening disease is prednisolone around 0.6 mg/kg daily for two to four weeks, followed by a structured taper over approximately three to six months.
Rituximab is an effective off-label steroid-sparing option for relapsing, refractory or high-risk disease, commonly 1 g IV on days 1 and 15 after HBV, infection, vaccine and immunoglobulin assessment.
Follow the organ that was ill, not serum IgG4 alone. Falling titre without improved obstruction, eGFR, imaging or gland and neurological function is not remission.

Key red flags

Fever, rigors, jaundice, hypotension or a dilated obstructed biliary tree suggests ascending cholangitis and requires antibiotics and urgent drainage before immune suppression.

Anuria, bilateral hydronephrosis, rapidly increasing creatinine or flank pain from retroperitoneal fibrosis requires immediate urological decompression.

Reduced acuity, colour desaturation, relative afferent pupillary defect, proptosis or painful restricted eye movement suggests optic or orbital compression.

Severe headache, cranial neuropathy, pituitary dysfunction, myelopathy or focal neurology raises pachymeningitis, hypophysitis or another central process.

A focal pancreatic, renal, pulmonary or salivary mass, vascular invasion, constitutional loss or atypical nodes must remain cancer until adequate tissue and multidisciplinary review say otherwise.

Chest, back or abdominal pain with aortic wall disease, aneurysm or periaortitis requires urgent vascular imaging because inflammation and structural rupture risk are separate decisions.

Retroperitoneal and vascular pattern

A periaortic soft-tissue mantle, ureteric encasement, hydronephrosis, inflammatory aneurysm or periarteritis indicates urgent structural mapping.

Orbital and neurological pattern

Proptosis, diplopia, infraorbital-nerve enlargement, optic dysfunction, pachymeningitic headache, cranial neuropathy or pituitary failure can threaten irreversible function.

Investigation priorities

First-line organ and biochemical mapFirst stepFirst line

Identify active sites, obstruction and a safe biopsy target before treatment.

Management branches

First diagnostic sequenceExclude cancer, map organs and preserve tissue

A pancreatic, glandular, orbital, renal or retroperitoneal lesion raises IgG4-related disease.

Stabilise cholangitis, renal obstruction, visual, neurological and vascular threats and obtain cross-sectional imaging of the presenting and common associated organs.
Measure serum and organ baselines, then select an architecture-preserving core from the safest representative site before glucocorticoid where possible.
Review radiology and pathology in an IgG4-experienced MDT, explicitly documenting malignancy, infection and organ-specific mimic exclusion.

First-line inductionUse glucocorticoid with an objective early checkpoint

Active symptomatic or organ-threatening disease is secure enough for treatment and untreated infection is excluded.

Start prednisolone about 0.6 mg/kg daily for two to four weeks with metabolic, bone, gastric and infection safeguards.
Measure early response in bilirubin or ducts, creatinine and imaging, orbital or neurological function and gland or lesion size, not symptoms or IgG4 alone.
Taper every one to two weeks toward withdrawal over three to six months, slowing or adding a steroid-sparing plan for high relapse risk.

Key medicines

PrednisoloneStart approximately 0.6 mg/kg orally once daily for two to four weeks in active disease, then reduce every one to two weeks toward cessation over about three to six months according to organ response and relapse risk.Monitor diabetes, pressure, mood, eyes, bone, infection and adrenal risk; failure to improve objectively should reopen diagnosis, obstruction and irreversible scar rather than trigger indefinite high dose.

RituximabGive 1000 mg intravenously on days 1 and 15 under an off-label IgG4-related disease protocol; retreatment is based on organ relapse and immune recovery rather than a fixed automatic cycle.Screen HBsAg and anti-HBc, TB and active infection, measure immunoglobulins, time vaccines and monitor infusion reaction, late neutropenia and hypogammaglobulinaemia.

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