HP and Huntington disease: CSF haptoglobin concentration of HD patients (0.9 [0.48 to 2.50] μg/ml) was significantly higher than those of controls (0.38 [0.22 to 0.53] μg/ml) (p = 0.014), whereas haptoglobin concentration in serum of HD patients (876 [799 to 2338] μg/ml) was not different from those of controls (902 [612 to 1846] μg/ml).