Differential Diagnosis of an Elevated Serum IgG4 Concentration

Differential diagnosis of elevated serum IgG4:

(1) IgG4-related disease

(2) atopic dermatitis

(3) asthma

(4) pemphigus

(5) multicentric Castleman's disease

(6) irritable bowel syndrome and/or food allergies

(7) malignancy (pancreatic cancer, hepatocellular carcinoma, other)

(8) filariasis

Serum IgG4 concentration can be expressed as:

(1) multiple of the upper limit of the normal reference range

(2) percent of total IgG (ratio of IgG4 to total IgG)

The serum concentration of IgG4 and the percent of total IgG tends to be higher in IgG4-related disease, but the diagnosis of IgG4-related disease requires other data to be present. The serum concentration of IgG4 in IgG4-related disease also tends to fall after treatment is started.