The mean level of serum ceruloplasmin in heterozygotes was (25.6 ± 5.9 mg/dL), significantly lower than that of healthy controls (30.7 ± 7.8 mg/dL, p < 0.05), but much higher than WD patients (5.7 ± 4.7 mg/dL, p < 0.001) (Fig. 1). Here, CP is linked to Wilson disease.