This study suggests that pre-treatment renal insufficiency and serum IgE elevation can be predictors of renal atrophy after glucocorticoid therapy, and that starting glucocorticoid therapy before eGFR declines to about 70 mL/min/1.73 m2 may be desirable in IgG4-RKD. The gene discussed is IGHE; the disease is Renal insufficiency.