Relationship between decrease in CCL18 plasma levels and chitotriosidase plasma activity. (A-B) Left panels show decrease in plasma CCL18 (▴) levels and plasma chitotriosidase activity (○) in individual patients on enzyme replacement therapy. Right panels show the relationship between the fractional changes in markers. (C) Relationship between fractional changes in markers following enzyme replacement therapy for at least 1 year. Excess activity at t = 0 was set at 100%. Depicted are results for 47 individual patients with Gaucher disease.