IgG4-Related Disease

**Semantic type:** Disease or Syndrome

**Definition:** An uncommon, mass-forming lesion that affects single or multiple sites. It is characterized by the presence of a lymphoplasmacytic infiltrate rich in IgG4-positive plasma cells and storiform tissue fibrosis, and increased serum IgG4 levels. It usually occurs in the pancreas, submandibular glands, lacrimal glands, lymph nodes, and hepatobiliary tract. Patients usually present with fatigue and weight loss. It responds to steroids treatment and follows a course of remissions and recurrences.

**Synonyms:** - IgG4-Related Sclerosing Disease - IgG4RD