Cross-sectional APRIL concentrations. (A) CSF APRIL, expressed as ng/mL (1000 × pg/mL). The pre-bundled treatment groups were ACTH (n = 33), steroids (n = 11), IVIg (n = 14), ACTH + IVIg (n = 29), steroids + IVIg (n = 14). (B) Serum APRIL, expressed as ng/mL. The three IVIg groups (IVIg, ACTH + IVIg, steroids + IVIg) did not differ significantly from each other in serum APRIL concentration, so they were combined into ‘All IVIg groups’. Compared to controls, the serum APRIL concentration was higher by 6.7-fold in the IVIg monotherapy group (32.6 ± 34 ng/mL), by 8.2-fold in the ACTH + IVIg group (39.9 ± 45 ng/mL), and by 6.9-fold in the steroid + other group (33.3 ± 26 ng/mL). IVIg was infused monthly, and most evaluations were scheduled just before the next IVIg was due.