COX15 and porphyria: Integrated pathway enrichment analysis identified down regulation of genes associated with porphyrias and porphyrin metabolism in kidney–specifically, heme biosynthetic enzymes uroporphyrinogen III synthase (UROS), uroporphyrinogen decarboxylase (UROD) and coproporphyrinogen III oxidase (CPOX), and Cytochrome c oxidase assembly protein COX15 homolog (COX15) also known as heme A synthase, a gene known to be regulated by porphyrin levels [71] and levels of metabolites in the plasma (S13 Table) and CSF (S14 Table).