Reduced serum caeruloplasmin levels in non-wilsonian movement disorders

Reduction in caeruloplasmin (Cp) levels is sometimes found in other sporadic movement disorders, not limited to Wilson's disease (WD). Serum levels of Cp, copper, iron and gamma-glutamyl transpeptidase were measured in 71 patients with various diagnoses of movement disorders, including Parkinson's disease (PD), atypical parkinsonian disorders, tardive dyskinesia, essential tremor, and idiopathic focal dystonia, and compared with those of 26 healthy age- and gender-matched controls. The mean Cp level in the patient group was 20.5 ± 4.2 mg/dl , lower than in controls (23.5 ± 7.2 mg/dl; p = 0.005). In subgroup analysis, mean Cp level of PD patients (19.6 ± 3.0 mg/dl) was lower than that of controls (p = 0.045). In a group analysis as neurodegenerative movement disorders (NDD), their mean Cp level was 19.9 ± 3.0 mg/dl, lower than that of controls (p = 0.019). Linear regression analysis indicated that the presence of NDD was the main factor associated with lower Cp levels. The finding of reduced serum Cp level in non-Wilsonian movement disorders and selective reduction in the neurodegenerative subgroup supports the notion that Cp might be associated with the cascade of neurotoxicity in NDD. The variation in Cp level in other non-WD conditions highlights the fact that Cp level is a poor screening test for WD in the absence of clear clinical suspicion.