Haptoglobin phenotype modifies serum iron levels and the effect of smoking on Parkinson disease risk

Introduction Haptoglobin is a hemoglobin-binding protein that exists in three functionally different phenotypes, and haptoglobin phenotype 2-1 has previously been associated with Parkinson disease (PD) risk, with mechanisms not elucidated. Some evidence is emerging that low levels of serum iron may increase PD risk. In this study we investigated whether PD patients have lower serum iron and ferritin than controls, and whether this is dependent on haptoglobin phenotype. We also investigated the effect of Hp phenotype as a modifier of the effect of smoking on PD risk.