This 14YO male is surprisingly asymptomatic with visual acuity of 20/30 OD and 20/40 OS. His retinal findings were found on a routine exam.
Optos imaging shows large, symmetrically bilateral, scalloped areas of chorioretinal atrophy that spare the central maculae.
On fundus autofluorescence (FAF), the scalloped areas of atrophy show hypo-FAF.
Swept-source OCT shows outer retinal and RPE atrophy within the clinical areas of atrophy.
The patient is adopted and is unaware of any family history of inherited retinal disease. Subsequent genetic testing revealed a pathogenic hemizygous CHM variant on the X chromosome, consistent with choroideremia.
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 can still develop clinical disease due to irregular inactivation of the X chromosome (see Jauregui et al, AJO 2019;207:77-86).
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 central island of vision, narrowed retinal vessels, and optic atrophy.
For a great choroid plexus review article, see Pennesi et al., Retina 2019;39:2019-2069.
