02/26/2026
This might be the only patient I see in my career with choroideremia, which is an X-linked inherited retinal degeneration that primarily affects males. The prevalence is about 1 in 50,000 -100,000. This teenage boy presented with progressively worsening night blindness and tunnel vision. They were referred for suspected retinitis pigmentosa, which has overlapping symptoms and clinical appearance. The scalloped appearance of peripheral chorioretinal atrophy (even more obvious on the Fundus autofluorescence photo) is more characteristic of choroideremia than RP.
Genetic testing revealed mutation in the CHM gene, which encodes for the REP1 protein, confirming the diagnosis. Dysfunction of this protein leads to gradual deterioration of the RPE, retina and choroid. These findings are evident in the macular OCT as well.
Unfortunately there is no treatment available for choroideremia, and the symptoms are expected to continue worsening overtime. Gene therapy studies were performed, with hopes of using a viral vector to restore function of the faulty REP1 protein. While the phase 3 results were generally positive, they did not meet their endpoint of a 3-line gain in visual acuity, which was required for FDA approval.
