|LETTER TO THE EDITOR
|Year : 2022 | Volume
| Issue : 1 | Page : 8
How to make a differential diagnosis between choroideremia and retinitis pigmentosa
Department of Clinical Ophthalmology, Institute of Ophthalmology, University College London, London, United Kingdom
|Date of Submission||16-Nov-2021|
|Date of Acceptance||25-Nov-2021|
|Date of Web Publication||09-Feb-2022|
Dr. Ali Nouraeinejad
Department of Clinical Ophthalmology, Institute of Ophthalmology, University College London, London, England
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Nouraeinejad A. How to make a differential diagnosis between choroideremia and retinitis pigmentosa. Pan Am J Ophthalmol 2022;4:8
|How to cite this URL:|
Nouraeinejad A. How to make a differential diagnosis between choroideremia and retinitis pigmentosa. Pan Am J Ophthalmol [serial online] 2022 [cited 2023 Jan 27];4:8. Available from: https://www.thepajo.org/text.asp?2022/4/1/8/337477
The term retinal dystrophy is used to describe a heterogeneous group of hereditary disorders in which the loss of photoreceptor function results in progressive visual impairment. The most common example is retinitis pigmentosa. One of the most important retinal dystrophies that may be confused with retinitis pigmentosa is choroideremia. Retinitis pigmentosa has broadly gained attention globally, but choroideremia is less heard.
Choroideremia is an X-linked recessive (XLR) inherited, bilateral progressive chorioretinal dystrophy/degeneration leading to blindness by late adulthood.,,,,,, It is caused by mutations in the CHM gene which encodes Rab escort protein-1.,,,,,, Choroideremia is evident as a progressive degenerative disorder of the photoreceptor layer, retinal pigment epithelium (RPE), and choroid.,, Areas of RPE atrophy are noticed early in the mid-periphery and then developed centrally. This is associated with the loss of photoreceptors and the choriocapillaris.
Preliminary symptoms of patients with choroideremia often include gradual decline in central visual acuity, nyctalopia, and constriction of the peripheral visual field. Nyctalopia is generally the first symptom often with onset during childhood.
Since choroideremia has an XLR pattern, male patients predominantly show the typical aspects of early nyctalopia during the first decade of childhood that advance into severe peripheral vision loss followed by legal blindness in late adulthood around the fifth to sixth decades.,,,, Nevertheless, although female carriers stay typically without symptoms, they can experience nyctalopia and show proof of pigmentary changes and chorioretinal degeneration in the fundus with coupled subnormal visual sensitivity.,,,,,, However, the chorioretinal degeneration built in female carriers is not obvious until typically the third to fourth decade.
X-linked inheritable retinal dystrophies exhibit a distinguishing family pedigree so that the course of the dystrophy differs between males and females., Choroideremia and X-linked retinitis pigmentosa are two of the most common X-linked inheritable retinal dystrophies. They share a variety of common clinical manifestations, including the same family pedigree, nyctalopia, constriction of the visual field (tunnel vision), gradually reduced visual acuity, and retinal degeneration., For this reason, it can be occasionally difficult to make a differential diagnosis between choroideremia and retinitis pigmentosa, which may lead to diagnostic confusion, especially in the absence of a typical fundus appearance.,, In this context, it is documented that about 6% of patients primarily diagnosed with retinitis pigmentosa in fact have choroideremia.
The author proposes for clinicians to consider the key classic triad of findings in retinitis pigmentosa that includes a bone spicule pigment migration pattern in the peripheral retina, optic disc pallor, and retinal vessel narrowing as well as another probable sign of epiretinal membrane formation.,,,,,
The degree of pigment migration into the retina that typifies retinitis pigmentosa is not seen in patients with choroideremia. In this respect, bilateral mid-peripheral intraretinal perivascular “bone spicule” pigmentary alterations and RPE atrophy related to arteriolar narrowing are noted in retinitis pigmentosa. In addition, a gradual rise in density of the pigment with anterior and posterior spread and a tessellated fundus appearance expands in patients with retinitis pigmentosa due to exposure to large choroidal vessels.
Moreover, retinitis pigmentosa may appear as a sporadic (simplex) disorder or be inherited in an autosomal dominant, autosomal recessive, or XLR mode. However, the mode of inheritance is only XLR in patients with choroideremia. The CHM gene is the only gene discovered in patients with choroideremia,, which can be proved by genetic analysis to counsel the family.
The author would like to express his honest gratitude and high respect for the lifetime support of his father, Mohammad Nouraeinejad.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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