Furthermore, the method can be used to monitor the in vivo expression patterns in patients under mRNA altering therapies like gene specific silencing RNAs (for example givosiran against ALAS1 in the acute hepatic porphyrias) or splice modulating oligos directed against FECH c.[315-48C] (Oustric et al., 2014; Halloy et al., 2020). This evidence concerns the gene FECH and Acute hepatic porphyria.