For instance, in patients with rickets, there is a decreased serum concentration of vitamin D metabolites owing to mutations in CYP3A4; in particular, the CYP3A4 I301T mutation results in a stronger activity inactivating vitamin D metabolites, thereby reducing levels of active vitamin D [375]; in other words, CYP3A4 polymorphisms can worsen some pathological conditions. Here, CYP3A4 is linked to rickets.