HMOX1 and dopa-responsive dystonia due to sepiapterin reductase deficiency: However, additional factors may be responsible for the high HO-1 levels found in patients with SRD, where a significantly higher increase of HO-1 plasma levels was observed between D0 and D28 in patients with SRD or SRD plus CM compared to other entities (p<0.0001, Kruskal Wallis test).