CHM encodes Rab escort protein-1 (REP-1), a crucial component of the Rab geranylgeranyltransferase complex responsible for protein prenylation and intracellular vesicle trafficking 1. REP-1 functions as the substrate-binding subunit that captures unprenylated Rab proteins and presents them to the catalytic components for geranylgeranyl transfer, enabling proper membrane targeting and vesicle-mediated transport. CHM mutations cause choroideremia, an X-linked chorioretinal dystrophy characterized by progressive degeneration of photoreceptors, retinal pigment epithelium, and choriocapillaris 21. The disease affects approximately 1 in 50,000-100,000 people, manifesting as night blindness in childhood that progresses to peripheral visual field loss and eventual complete blindness 2. Most pathogenic variants represent loss-of-function mutations, including large genomic deletions, insertions/deletions, nonsense variants, and splice site mutations, with a notable prevalence of C-to-T transitions at CpG dinucleotides 34. The high frequency of null mutations makes choroideremia particularly suitable for gene replacement therapy approaches, with ongoing clinical trials showing promise for treatment 31.