The KEGG pathway analysis showed seven metabolic pathways that were enriched in neurosyphilis patients compared to syphilis/non-neurosyphilis patients; these pathways included tryptophan metabolism, biosynthesis of unsaturated fatty acids, fatty acid biosynthesis, lysosome, ABC transporters, fructose and mannose metabolism, and galactose metabolism (Figure 6A). Here, ABCG2 is linked to neurosyphilis.