QUIZ: No. 34, 08/11/2025

QUIZ No. 34

ANS – IgG4 related Infraorbital nerve enlargement (IgG4 IONE) + Paranasal sinus disease + Extraocular muscle enlargement + Enlarged lacrimal glands 🡪 IgG4-related orbital disease

Findings: Well-defined soft tissue lesion along the bilateral infraorbital nerve (R>>L), extending from the pterygopalatine fossa to the infraorbital foramen. Smooth enlargement of the infraorbital canal without bony erosion. No mass effect on extraocular muscles or globe deformity. MRI: Lesion is isointense on T1, hypointense on T2, and shows homogeneous enhancement post-contrast. No diffusion restriction or necrosis. Asymmetric extraocular muscle enlargement. Paranasal sinus disease. Enlarged lacrimal gland.

IgG4-related disease is a chronic fibroinflammatory condition characterized by dense lymphoplasmacytic infiltration, storiform fibrosis, and IgG4+ plasma cells.
It can involve lacrimal glands, salivary glands, pancreas, retroperitoneum, and orbit.

Take home points

1. Infraorbital nerve enlargement with smooth enhancement and no bone destruction is a distinctive feature of IgG4-related orbital disease.

2. Tendon sparing, T2 hypointensity, and homogeneous enhancement favor IgG4-related fibrosis.

3. Always correlate with serum IgG4 levels and histopathology.

4. Early steroid therapy can prevent irreversible fibrosis and vision loss.