The reduction in the enzymatic activity of the encoded porphobilinogen deaminase (PBGD, EC 2.5.1.61; MIM#609806), combined with other triggering factors (nutritional, hormonal, drugs, or infections), leads to a critical deficiency in the “heme regulatory pool” or stimulates heme synthesis through PGC-1α activation, which results in ALA and PBG accumulation and subsequent attacks [22,23]. This evidence concerns the gene HMBS and infection.