IMPDH1 and autosomal dominant retinitis pigmentosa: It is interesting to note that causative variants in the gene inosine monophosphate dehydrogenase 1 (IMPDH1), which controls the rate-limiting step in GTP production, are also linked to autosomal dominant retinitis pigmentosa (Bowne et al., 2002; Aherne et al., 2005; Mortimer and Hedstrom, 2005; Spellicy et al., 2010; Bennett et al., 2020).