IgG4-Related Disease¶
Chapter 380 | Part 11: Immune-Mediated, Inflammatory, and Rheumatologic Disorders
KEY CLINICAL POINTS¶
- IgG4-related disease (IgG4-RD) is a fibroinflammatory condition characterized by variable-vessel vasculitis and fibrosis, affecting multiple organs.
- Key clinical features include tumefactive lesions, elevated serum IgG4 levels, and involvement of the pancreas, salivary glands, retroperitoneum, and lungs.
- Diagnosis requires integration of clinical, serologic, radiologic, and histopathologic findings, with IgG4-positive plasma cells and storiform fibrosis as hallmark features.
- Treatment typically begins with glucocorticoids, with rituximab as a second-line option for refractory disease.
- Prognosis varies; complications include organ failure, renal dysfunction, and aortic aneurysms, necessitating long-term monitoring.
1. DEFINITION & OVERVIEW¶
IgG4-related disease (IgG4-RD) is a systemic fibroinflammatory condition characterized by a tendency to form tumefactive lesions and fibrosis. It is classified as a variable-vessel vasculitis due to its ability to target blood vessels of any size. The disease can affect virtually any organ system, including the pancreas, salivary glands, retroperitoneum, lungs, and kidneys. Clinical manifestations are protean, with a predilection for forming mass lesions that may mimic malignancies.
Table 380-1 Organ Manifestations of IgG4-Related Disease¶
| ORGAN | MAJOR CLINICAL FEATURES |
|---|---|
| Orbits and periorbital tissues | Painless eyelid or periocular tissue swelling; orbital pseudotumor; dacryoadenitis; dacryocystitis; orbital myositis; and mass lesions extending into the pterygopalatine fossa and infiltrating along the trigeminal nerve |
| Ears, nose, and sinuses | Allergic phenomena (nasal polyps, asthma, allergic rhinitis, peripheral eosinophilia); nasal obstruction, rhinorrhea, anosmia, chronic sinusitis; occasional bone-destructive lesions |
| Salivary glands | Submandibular and/or parotid gland enlargement (isolated bilateral submandibular gland involvement more common); minor salivary glands sometimes involved |
| Meninges | Headache, radiculopathy, cranial nerve palsies, or other symptoms resulting from spinal cord compression; tendency to form mass lesions; magnetic resonance imaging (MRI) shows marked thickening and enhancement of dura |
| ORGAN | MAJOR CLINICAL FEATURES |
|---|---|
| Hypothalamus and pituitary | Clinical syndromes resulting from involvement of the hypothalamus and pituitary, e.g., anterior pituitary hormone deficiency, central diabetes insipidus, or both; imaging reveals thickened pituitary stalk or mass formation on the stalk, swelling of the pituitary gland, or mass formation within the pituitary |
| Lymph nodes | Generalized lymphadenopathy or localized disease adjacent to a specific affected organ; the lymph nodes involved are generally 1–2 cm in diameter and nontender |
| Thyroid gland | Riedel’s thyroiditis; fibrosing variant of Hashimoto’s thyroiditis |
| Lungs | Asymptomatic finding on lung imaging; cough, hemoptysis, dyspnea, pleural effusion, or chest discomfort; associated with parenchymal lung involvement, pleural disease, or both; four main clinical lung syndromes: inflammatory pseudotumor, paravertebral mass often extending over several vertebrae, central airway disease, localized or diffuse interstitial pneumonia; pleural lesions have severe, nodular thickening of the visceral or parietal pleura with diffuse sclerosing inflammation, sometimes associated with pleural effusion |
| Aorta | Asymptomatic finding on radiologic studies; surprise finding at elective aortic surgery; aortic dissection; clinicopathologic syndromes described include lymphoplasmacytic aortitis of thoracic or abdominal aorta, aortic dissection, periaortitis and periarteritis, and inflammatory abdominal aneurysm |
| Retroperitoneum | Backache, lower abdominal pain, lower extremity edema, hydronephrosis from ureteral involvement, asymptomatic finding on radiologic studies. Classic radiologic appearance is periaortic inflammation extending caudally to involve the iliac vessels. |
| Kidneys | Tubulointerstitial nephritis; membranous glomerulonephritis in a small minority; asymptomatic tumoral lesions, typically multiple and bilateral, are sometimes detected on radiologic studies; renal involvement strongly associated with hypocomplementemia |
| Pancreas | Type 1 autoimmune pancreatitis, presenting as mild abdominal pain; weight loss; acute, obstructive jaundice, mimicking adenocarcinoma of the pancreas (including a pancreatic mass); between 20 and 50% of patients present with acute glucose intolerance; imaging shows diffuse (termed "sausage-shaped pancreas") or segmental pancreatic enlargement, with loss of normal lobularity; a mass often raises the suspicion of malignancy |
| Biliary tree and liver | Obstructive jaundice associated with autoimmunity in most cases; weight loss; steatorrhea; abdominal pain; and new-onset diabetes mellitus; mimicker of primary sclerosing cholangitis and cholangiocarcinoma |
| ORGAN | MAJOR CLINICAL FEATURES |
|---|---|
| Other organs involved | Gallbladder, liver (mass), breast (pseudotumor), prostate (prostatism), pericardium (constrictive pericarditis), mesentery (sclerosing mesenteritis), mediastinum (fibrosing mediastinitis), skin (erythematous or flesh-colored papules), peripheral nerve (perineural inflammation) pancreatic failure and the resulting inability of the pancreas to produce sufficient quantities of digestive enzymes. Failure of the endocrine pancreas, resulting in diabetes mellitus, is also common. |
1.1 Clinical Spectrum¶
IgG4-RD encompasses a spectrum of conditions previously considered separate entities, including lymphoplasmacytic sclerosing pancreatitis, Mikulicz’s disease, and retroperitoneal fibrosis. The disease often presents subacutely with non-specific symptoms, and multiorgan involvement is common.
1.2 Diagnostic Criteria¶
Diagnosis requires integration of clinical, serologic, radiologic, and histopathologic findings. Key criteria include elevated serum IgG4 levels (>135 mg/dL), tissue infiltration with IgG4-positive plasma cells (>10% of plasma cells), storiform fibrosis, and obliterative phlebitis. Biopsy is not required in classic cases but is often performed to exclude malignancy.
2. EPIDEMIOLOGY¶
The typical patient with IgG4-RD is a middle-aged to elderly man. This epidemiology contrasts with classic autoimmune conditions, which often affect young women. Male patients are approximately 5 years older at diagnosis and have higher serologic activity (e.g., IgG4 hypergammaglobulinemia or hypocomplementemia). The male-to-female ratio is ~2:1, with male predominance in certain internal organ manifestations. The disease is more common in individuals with allergic features (atopy, eczema, asthma) and may present with multiorgan involvement.
2.1 Risk Factors¶
Allergic disease, genetic predisposition, and environmental factors may contribute. Patients with IgG4-RD often have a history of allergic phenomena (nasal polyps, asthma, sinusitis) and peripheral eosinophilia. The prozone effect may lead to falsely low IgG4 levels in cases of extremely high concentrations.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
IgG4 is not directly pathogenic but may act as a counterregulatory mechanism. The disease involves CD4+ cytotoxic T cells producing profibrotic cytokines (IFN- γ , TGF- β , IL-1) and B-cell-derived plasmablasts. Fab exchange reduces IgG4 affinity for Fc receptors and C1q, limiting its inflammatory potential. Pathologic features include lymphoplasmacytic infiltrates, storiform fibrosis, obliterative phlebitis, and mild eosinophilia.
3.1 Molecular Mechanisms¶
CD4+ cytotoxic T cells and B-cell-derived plasmablasts drive fibrosis. Continuous antigen presentation by B cells supports T-cell activity, leading to tissue injury. Oligoclonal expansion of CD4+ T cells and plasmablasts is a hallmark. The prozone effect may cause false-negative IgG4 results in cases of extreme elevation.
4. CLINICAL FEATURES¶
Symptoms vary by organ involvement. Common presentations include painless eyelid swelling, submandibular gland enlargement, and retroperitoneal pain. Systemic symptoms may include weight loss, fatigue, and fever. Complications include renal failure, aortic aneurysms, and obstructive jaundice. The disease may evolve over months to decades before severe manifestations occur.
4.1 Organ-Specific Manifestations¶
Pancreatic involvement presents as obstructive jaundice or mass lesions. Retroperitoneal fibrosis causes hydronephrosis and lower extremity edema. Lymphadenopathy and orbital pseudotumors are common. Neurological features include cranial nerve palsies and meningitis-like symptoms.
5. DIFFERENTIAL DIAGNOSIS¶
IgG4-RD must be differentiated from malignancies, granulomatosis with polyangiitis, and other autoimmune diseases. Key distinguishing features include the absence of granulomas, the presence of storiform fibrosis, and the response to immunosuppressive therapy. Allergic features and the pattern of organ involvement aid in differentiation.
6. INVESTIGATIONS & DIAGNOSIS¶
Serum IgG4 levels are elevated in most patients (>135 mg/dL), though normal values may occur in some cases. Imaging (MRI, CT) reveals characteristic findings such as periaortic inflammation, pancreatic enlargement, and pleural thickening. Biopsy shows IgG4-positive plasma cells (>10%), storiform fibrosis, and obliterative phlebitis. The prozone effect may require serum dilution for accurate IgG4 quantification.
6.1 Diagnostic Algorithms¶
- Assess clinical features (organ involvement, allergic symptoms). 2. Measure serum IgG4 and complement levels. 3. Perform imaging to identify characteristic lesions. 4. Biopsy for histopathologic confirmation (IgG4-positive plasma cells, storiform fibrosis). 5. Exclude malignancy and other autoimmune diseases.
7. MANAGEMENT & TREATMENT¶
Glucocorticoids (e.g., 40 mg/d prednisone) are first-line therapy, with tapering to 5 mg/d over 2–3 months. Rituximab (2 g IV, two doses separated by ~15 days) is effective for refractory cases. Other agents include mycophenolate mofetil, leflunomide, and TNF inhibitors (infliximab). Long-term monitoring is essential due to risk of relapse and organ damage.
7.1 Treatment Algorithms¶
- Initiate glucocorticoids for active disease. 2. Use rituximab for refractory or relapsing cases. 3. Consider immunosuppressants (mycophenolate, leflunomide) for maintenance. 4. Monitor for complications (renal failure, aortic aneurysms). 5. Adjust therapy based on serum IgG4 levels and organ function.
8. PROGNOSIS & COMPLICATIONS¶
Prognosis varies; severe complications include renal failure, aortic dissection, and hepatic failure. Early diagnosis and treatment improve outcomes. Untreated disease may lead to irreversible organ damage. Long-term corticosteroid use increases risk of osteoporosis and infections.
8.1 Complications¶
Renal dysfunction, aortic aneurysms, obstructive jaundice, and fibrotic lung disease are common. Untreated IgG4-related sclerosing cholangitis may progress to hepatic failure within months. Postobstructive uropathy and renal atrophy are frequent sequelae.
9. SPECIAL CONSIDERATIONS¶
Pregnancy and breastfeeding require careful monitoring due to corticosteroid use. Elderly patients are at higher risk for infections and osteoporosis. Pediatric cases are rare but may present with similar features. Patients with renal involvement require close monitoring for hypocomplementemia and tubulointerstitial nephritis.
9.1 Pregnancy and Lactation¶
Corticosteroids are generally safe in pregnancy but require monitoring for fetal growth. Breastfeeding is possible with low-dose corticosteroids. Rituximab is contraindicated in pregnancy due to potential teratogenic effects.
10. KEY POINTS & CLINICAL PEARLS¶
- IgG4-RD is a systemic fibroinflammatory disease with variable-vessel vasculitis.
- Diagnosis requires integration of clinical, serologic, and histopathologic findings.
- Elevated serum IgG4 (>135 mg/dL) is a key biomarker but not diagnostic alone.
- Glucocorticoids are first-line therapy, with rituximab as a second-line option.
- Monitor for complications (renal failure, aortic aneurysms) and long-term steroid toxicity.
- Biopsy is essential for definitive diagnosis, especially in cases with atypical presentations.