IgG4-related disease

IgG4-related disease (IgG4-RD) is a chronic inflammatory condition characterized by tissue infiltration with IgG4-positive plasma cells and T lymphocytes, leading to fibrosis and the formation of tumefactive lesions in various organs. This disease can affect multiple organ systems, often presenting with a wide range of clinical manifestations.

Clinical Features

IgG4-RD can involve almost any organ system, but commonly affected sites include the pancreas, biliary tree, salivary glands, orbit, kidneys, lungs, and retroperitoneum. The clinical presentation varies depending on the organs involved. Common symptoms include:

• Jaundice and abdominal pain in cases involving the pancreas and biliary tree.
• Xerostomia and xerophthalmia when the salivary and lacrimal glands are affected.
• Proptosis and orbital mass in orbital involvement.
• Renal dysfunction and proteinuria in renal involvement.

Pathophysiology

The pathogenesis of IgG4-RD is not fully understood, but it is believed to involve an abnormal immune response. The hallmark of the disease is the presence of IgG4-positive plasma cells in the affected tissues. This is accompanied by a dense lymphoplasmacytic infiltrate, storiform fibrosis, and obliterative phlebitis. Elevated serum IgG4 levels are often observed, although this is not specific to the disease.

Diagnosis

The diagnosis of IgG4-RD is based on a combination of clinical, serological, and histopathological findings. Key diagnostic criteria include:

• Elevated serum IgG4 levels.
• Histopathological evidence of IgG4-positive plasma cell infiltration and storiform fibrosis.
• Imaging findings consistent with organ involvement.

Treatment

The mainstay of treatment for IgG4-RD is glucocorticoids, which are effective in reducing inflammation and inducing remission. In cases where patients are refractory to steroids or require long-term treatment, other immunosuppressive agents such as rituximab, azathioprine, or mycophenolate mofetil may be used.

Prognosis

The prognosis of IgG4-RD varies depending on the extent and severity of organ involvement. Early diagnosis and treatment are crucial to prevent irreversible organ damage. Most patients respond well to glucocorticoid therapy, but relapses are common, necessitating long-term follow-up.

See Also

• Autoimmune disease
• Inflammation
• Plasma cell
• Fibrosis