Choroideremia (CHM, OMIM 303100) is a distinct diagnosis that can be clinically distinguished from other retinal degenerations, such as other forms of retinitis pigmentosa (RP). CHM represents 6% of cases in one practice that focused on RP-related conditions.¹⁰ Mauthner first used the term to indicate that the choroid was missing while the retinal vessels were preserved and no optic atrophy was noted.¹⁴ These characteristics set CHM apart from RP, which has significant pigment dispersion in the retina, retinal vessel narrowing, and optic nerve gliosis. In some cases, patients with CHM have posterior subcapsular cataracts that are also commonly seen in RP. CHM is an ocular disorder with no systemic manifestations. The extensive study of a large Canadian family with CHM by McCulloch and McCulloch in 1948 indisputably showed CHM to be X-linked.¹⁵