A preauricular erythematous indurated plaque.

A serum IgG4 concentration greater than 1.35 g L SP -1 sp is suggestive of IgG4-RD.[3] Histological features of IgG4-RD include a dense lymphoplasmacytic infiltrate, storiform fibrosis and obliterative phlebitis. A 55-year-old woman presented with a 7-month history of an erythematous plaque affecting the right preauricular skin and ipsilateral swelling of the ear. The diagnosis of IgG4-RD relies on a combination of clinical, histopathological, radiographical and serological features.[3] Common laboratory abnormalities include elevated serum IgG4, serum IgE and eosinophilia.[5] The degree of serum IgG4 elevation correlates with the number of organs involved; however, a significant minority of patients will have a normal serum IgG4. [Extracted from the article]