• IgG4-related disease is a fibroinflammatory disease that tends to form mass-like lesions.
• It can affect almost any organ system. However, it is not expected to involve the brain parenchyma, bone marrow, joints and intestinal mucosa.
• The disease is most common in middle-aged and elderly men.
Pathology
• Basic pathological features in all organs affected by this disease;
o Lymphoplasmocytic infiltration with a high percentage of IgG4 (+) plasma cells
o Characteristic fibrosis called "Storiform" (basket weave-like)
o Tendency to target blood vessels (obliterative phlebitis, especially in veins)
o Inflammation that tends to surround the ducts of the involved gland (lacrimal, salivary and pancreatic)
o Mild to moderate tissue eosinophilia
Clinical Findings
• Two common characteristics of IgG4 systemic disease;
o Allergic disease: Most patients have atopy, eczema, asthma, sinusitis and eosinophilia.
o Massive lesions mimicking malignancy: Patients may be mistakenly diagnosed with malignancy
IgG4-related disease involvement
Orbital and periorbital tissues:
Eyelid and periorbital edema, orbital pseudotumor, dacryoadenitis,
dacryocystitis
Ear, nose and sinuses:.
Allergic phenomena (bronchial asthma, allergic rhinitis, sinusitis), nasal obstruction, rhinorrhea, anosmia and sometimes bone destruction
salivary glands:
Submandibular/parotid growth
Meninges :
Headache, radiculopathy, cranial nerve palsy, dural thickening
Hypothalamus and pituitary gland:
Pituitary insufficiency, central diabetes insipidus, mass in the pituitary stalk
Thyroid gland: Riedel's thyroiditis
Lymph nodes: Diffuse/local lymphadenopathy
Lungs: Cough, hemoptysis, dyspnea, pleural effusion, inflammatory
pseudotumor, localized/diffuse interstitial pneumonia, central airway
disease, pleuritis
Aorta: Aortic dissection, periaortitis, inflammatory abdominal aorta
aneurysm
Retroperitoneum: Low back pain, pain in the lower abdomen, hydronephrosis
Kidneys: Tubulointerstitial nephritis, membranous nephropathy, hypocomplementemia
Pancreas: Type I autoimmune pancreatitis, mass appearance in the pancreas, obstructive jaundice
Bile ducts and liver: Obstructive jaundice, abdominal pain, steatorrhea, weight loss, new-onset diabetes mellitus, findings mimicking primary sclerosing cholangitis
Serological findings
• The majority of patients have high serum IgG4 levels.
• Serum IgG4 level does not correlate well with disease activity and treatment requirement.
Treatment
• Glucocorticoids are the first-line treatment option.
• Rituximab is the second-line treatment option in patients with frequent relapses or steroid-resistant patients.