IgG4-related disease (IgG4-RD) is an autoimmune disease triggering an inflammatory cascade that leads to fibrosis. Outcome measures are limited and treatment options remain underexplored.

To assess the variation of the IgG4 responder index (IgG4-RI) in a cohort of IgG4-RD patients and to explore their treatments and outcomes.

We studied the clinical phenotype, severity of the disease and response to treatment in an ambispective multicenter cohort study including 14 different hospitals in Spain. All patients met the 2012 international consensus on pathology criteria for diagnosis.

Sixty-eight patients were included, with a mean age of 53.4 years and predominance of male sex. The most commonly involved tissues were: retroperitoneum (33%), orbital pseudotumor (28%) and maxillary and paranasal sinuses (24%). IgG4-RI values were higher in patients with multiorgan disease and before treatment. After being treated, IgG4-RI values were lower, in accordance with the high rates of treatment response. Most patients received: glucocorticoids (GC), surgery, azathioprine (AZA), mofetil mycophenolate or rituximab. GC alone, GC plus surgery and GC plus AZA were given in the most of the IgG4-RD disease activity episodes. All treatments had high response rates but relapses and flares were common.

IgG4-RI is a promising outcome measure in IgG4-RD, but still in development. Treatment algorithms are ill defined. GC and rituximab are the drugs with more evidence available. Disease modifying anti-rheumatic drugs may have a role in IgG4-RD and warrant more prospective studies.