Scheme of the effect of Gaucher disease on biomarkers and the effect of ERT. A: Mechanistic pathophysiological model. Plus sign (+) indicates stimulation and minus sign (−) indicates inhibition. C is chitotriosidase produced at a rate of R and removed at a rate of λ B: Simplified model of changes in biomarkers during ERT. Left: biomarkers that decrease during ERT (ferritin, chitotriosidase); right: biomarkers that increase during ERT (hemoglobin, platelets). C0 is initial concentration, k rate of decrease (or increase) and C0r estimated corrected value at steady state of ERT.