Choroideremia (CHD) is a rare X-linked recessive inherited disorder giving rise to retinal disease and eventual blindness, resulting from degeneration of the choriocapillaris of the choroid and of the retinal pigment epithelium of the retina. The disease results in progressive loss of vision, almost exclusively in males; in childhood, night blindness is the most common first symptom.[not verified in body] As the disease progresses, vision loss results, frequently starting as an irregular ring that gradually expands both in toward central vision and out toward the extreme periphery; progression continues throughout the individual's life, where both the rate of change and the degree of visual loss are variable among those affected, even within the same family.
- Night blindness
- Loss of peripheral vision
- Reduced central vision
- Mental retardation
- Progressive vision loss
- Atrophy of retinal layers
There is a genetic blood test to diagnose Choroideremia. It was created by Dr. Ian MacDonald at the University of Alberta. Free genetic testing is available for US and Canadian Residents through the eyeGENE project which is coordinated by the National Eye Institute at the US National Institutes of Health. Human gene therapy trials are underway at the Imperial College of London under the direction of Dr. Miguel Seabra and at Moorfields Eye Hospital in London under the direction of Dr. Robert MacLaren. In the United States preclinical trial work is underway at the University of Pennsylvania under the direction of Dr. Jean Bennett and Dr. Albert Maguire. Dr. Ian MacDonald is also pursuing clinical trials at the University of Alberta in Canada. The Choroideremia Research Foundation, an international non-profit organization that for over ten years has been dedicated to raising awareness and securing funding for choroideremia research, is currently funding pre-clinical trial work for Dr. Seabra and Dr. Bennett. Dr. Ian MacDonald also serves on the board of directors for the CRF and receives funding from CRF-Canada. Human clinical trials are expected to start in the US in 2014. CRF-Canada also supports Dr. Seabra's and Dr. MacLaren's work as does Fight for Sight (UK).
The prognosis of Choroideremia usually refers to the likely outcome of Choroideremia. The prognosis of Choroideremia may include the duration of Choroideremia, chances of complications of Choroideremia, probable outcomes, prospects for recovery, recovery period for Choroideremia, survival rates, death rates, and other outcome possibilities in the overall prognosis of Choroideremia. Naturally, such forecast issues are by their nature unpredictable.
Robert E MacLaren, Professor of Ophthalmology, and investigator at the Nuffield Laboratory of Ophthalmology at the University of Oxford, and colleagues there and at the John Radcliffe Hospital in Oxford have used a gene therapy protocol—first attempted at Moorfields Eye Hospital in London —to attempt to treat the choroideremic REP1 deficiency that leads to degeneration of the choriocapillaris and retinal pigment epithelium and loss of light sensitivity, and eventually, sight. The objectives of the protocol, funded by the U.K.'s Health Innovation Challenge Fund were to "assess the safety and tolerability of the AAV.REP1 vector" used to introduce the replacement REP1 gene, through its administration to the retinas of 12 choroideremia patients at 2 doses, and secondarily, to seek to observe therapeutic benefit during the study, and at a 24-month post-treatment time point, based on functional and anatomical tests to evaluate any "slowing down of… retinal degeneration" in treatment versus control groups. The work is an outgrowth of an earlier, promising gene therapy approach to treat Leber congenital amaurosis (LCA), where this effort attempts to introduce new, functioning copies of the REP1 gene to the eye using an adenoviral vector, so to halt cell death associated with this deficiency; the trial gave initial, promising results in January 2014: all of the 6 patients in the treatment group (those receiving the gene replacement) had degeneration to varying degrees before the treatment, and all described vision improvement. Work is underway in this trial to determine the persistence of the therapeutic improvements that were initially observed.