Aldh4a1 belongs to the aldehyde dehydrogenase superfamily, and it is associated with type II hyperprolinemia (HPII) (Geraghty, et al., 1998; van de Ven, et al., 2014), whose patients suffer from fibroblast mitochondrial dysfunction. This evidence concerns the gene ALDH4A1 and hyperprolinemia type 2.