IgG4-related disease of the mastoid: a rare presentation of a novel diagnosis.

IgG-related disease (IgG-RD) is an inflammatory condition characterised by infiltration of tissue by IgG-positive plasma cells. This is the seventh reported case of IgG-RD affecting the mastoid and informs clinicians in diagnosing patients affected by this rare condition.A woman in her 20s presented with unilateral otalgia, hearing loss and vertigo.