In affected twins, we observed a decreasing trend for Al, Co and Sr, especially in the case of Co (medians, 0.15 vs. 0.37 ng/ml, at a p=0.06) and a tendency to higher concentrations for Zn (medians, 883 vs. 818 ng/ml, p=0.10) and Be (0.48 vs. 0.40 ng/ml, p=0.18).