LEARNING OBJECTIVES:
1. To discuss the common and uncommon multi-organ manifestations of immunoglobulin G4-related disease (IgG4-RD). 
2. To understand the indications, challenges, and pitfalls of various cross-sectional imaging modalities, including MDCT, MRI, and US, in the diagnosis and evaluation of IgG4-RD. 
3. To review the spectrum of imaging findings, mimics, and differential diagnosis of IgG4-RD from head-to-toe.

BACKGROUND: IgG4-RD is an autoimmune disorder characterized by infiltration of organs with IgG4-positive plasma cells resulting in fibro-inflammatory lesions in one or more organ systems. Although the pancreas is the most commonly affected organ, involvement of extra-pancreatic organs is increasingly recognized as a key manifestation of the disease. Patients are often asymptomatic and serum IgG4 concentrations may be normal. Treatment consists of the utilization of corticosteroids. Although a definitive diagnosis requires histopathology, imaging plays an essential role in guiding appropriate management. 

CONCLUSION: Knowledge of the varied imaging findings of this multi-system disease is essential for radiologists to avoid misdiagnosis and assist with timely and effective treatment.

IgG4-RELATED DISEASE: CURRENT STATUS AND FUTURE DIRECTIONS