A young woman with steroid-responsive, IgG4-positive plasma cell-enriched cystic lymphangioma and chylous ascites.

Lymphangiomas are benign tumors of the lymphatic vessels, which can be inflammatory and occasionally steroid-responsive. IgG4-related disease (IgG4-RD) is a recently defined fibro-inflammatory condition. We describe a novel association between reactive IgG4+ plasma cells and cystic lymphangioma in a young woman who had a dramatic clinical response to steroids.