This 27YO female has a known history of choroideremia and is heterozygous for a pathogenic CHM mutation. Vision was 20/150 OD and 20/30 OS.
Color imaging shows large, symmetrically bilateral, scalloped areas of chorioretinal atrophy that spare the central maculae. Some peripheral areas of intraretinal pigment migration (bone spicules) are noted as well. OCT scanning shows variable outer retinal loss on B-scan with a scalloped preserved central macula on en face.
Learning Points:
Choroideremia is an X-linked recessive chorioretinal dystrophy caused by a mutation in the CHM gene located on the long arm of the X chromosome. Sons of female carriers have a 50% chance of developing choroideremia, and daughters have a 50% chance of becoming carriers. Some female carriers, as in our patient, can still develop choroideremia due to irregular inactivation of the X chromosome (see Jauregui et al, AJO 2019;207:77-86).
The onset of night blindness usually begins between the ages of 10 and 30, followed by peripheral visual field loss. Zones of patchy RPE and chorioretinal atrophy initially appear in the mid-periphery, gradually spreading anteriorly and posteriorly. Eventually, the patient is left with only a small island of vision, narrowed retinal vessels, and optic atrophy.
