1993). CHM is only known to be caused by mutations in the CHM gene affecting the expression of Rab escort protein 1 (REP‐1), which is an important part of the pathways that enable the prenylation of Rab proteins that are essential for intracellular trafficking (Cremers et al. 1990b; Merry et al. 1992). There are 136 reported pathogenic variants in the CHM gene associated with the CHM phenotype (Leiden Open Variant CHM Database, http://www.lovd.nl/CHM [accessed June 2015]). The gene discussed is CHM; the disease is choroideremia.