|Year : 2014 | Volume
| Issue : 3 | Page : 114-117
An interesting case of "bear track dystrophy"
Avinash Mishra1, Somesh Aggarwal2, Sonali Shah2, Puja Negi2
1 Department of Ophthalmology, Military Hospital, Ahemdabad, Gujarat, India
2 Department of Retina, M and J Western Regional Institute of Ophthalmology, Ahemdabad, Gujarat, India
|Date of Web Publication||7-Sep-2015|
Dr. Avinash Mishra
Military Hospital Ahemdabad, Ahemdabad, Gujarat
Source of Support: Nil, Conflict of Interest: None declared.
Bear track dystrophy, is a rare condition, which forms part of the disorder known as the grouped congenital hypertrophy of the retinal pigment epithelium (CHRPE), a peculiar congenital anomaly of the retinal pigment epithelium diagnosed by its characteristic ophthalmoscopic appearance. This disorder is usually without any functional consequence with patients typically having a normal vision, color vision, normal visual fields, dark adaptation, electroretinography, and electrooculography findings. The main differential diagnosis of CHRPE includes choroidal naevus, choroidal melanoma, chorioretinal scar, subretinal hematoma, pigmented epiretinal membrane, and reactive retinal pigment epithelial hyperplasia. Since CHRPE, in itself is a totally benign condition with no associated ocular or systemic complications, it becomes that much more important to distinguish it from the more serious vision/life-threatening conditions like choroidal melanoma as well as from the other pigmented ocular fundus lesions associated with familial cancer syndromes like familial adenomatous polyposis.
Keywords: Choroidal melanoma, congenital hypertrophy of the retinal pigment epithelium, normal vision, pigmented ocular fundus lesions
|How to cite this article:|
Mishra A, Aggarwal S, Shah S, Negi P. An interesting case of "bear track dystrophy". Egypt Retina J 2014;2:114-7
| Introduction|| |
Bear track dystrophy, is a rare condition, which forms part of the disorder known as the grouped congenital hypertrophy of the retinal pigment epithelium (CHRPE), a peculiar congenital anomaly of the retinal pigment epithelium (RPE) diagnosed by its characteristic ophthalmoscopic appearance. This disorder is usually without any functional consequence with patients typically having a normal vision, color vision, normal visual fields, dark adaptation, electroretinography, and electrooculography findings.
The main differential diagnosis of CHRPE includes choroidal naevus, choroidal melanoma, chorioretinal scar, subretinal haematoma, pigmented epiretinal membrane, and reactive retinal pigment epithelial hyperplasia.
Since CHRPE, in itself is a totally benign condition with no associated ocular or systemic complications, it becomes that much more important to distinguish it from the more serious vision/life threatening conditions like choroidal melanoma as well as from the other pigmented ocular fundus lesions (POFL's) associated with familial cancer syndromes like familial adenomatous polyposis (FAP).
| Case Report|| |
A 41-year-old lady, reported for a routine eye examination for the very 1st time, without having any obvious ocular/systemic signs or symptoms. Her vision was a normal 6/6 in both eyes. The anterior segment findings too were well within normal limits. The visual fields (confrontation method) and the color vision, evaluated using an Ishihara chart, too were normal. However, a dilated fundoscopy revealed multiple, segmentally oriented, distinct, well demarcated, flat, hyper pigmented, greyish black lesions in the retina. These were smaller around the optic disc and gradually became larger in size towards the periphery. Similar findings were seen in both her eyes. A provisional diagnosis of congenital hypertrophy of the retinal pigment epithelium (CHRPE) both eyes was made and the patient was subjected to a fundus photography to further confirm the diagnosis. The picture in the right eye [Figure 1] revealed multiple hyperpigmented, flat, clearly demarcated patches resembling animal foot prints. These were more in number and size in the peripheral retina [Figure 2]a and [Figure 2]b. A similar picture was seen in the left eye too [Figure 3] and [Figure 4]. The macula was sparred in both eyes. The rest of the fundus including the optic disc was normal.
|Figure 1: Fundus photograph-right eye - multiple hyperpigmented, flat clearly demarcated patches resembling animal foot prints|
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|Figure 2: (a and b) Fundus photograph-right eye - hyperpigmented lesions seen to be more in number and size in the peripheral retina|
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|Figure 3: Fundus photograph-left eye - similar hyperpigmented lesions seen in the left eye also|
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|Figure 4: Fundus photograph-left eye - in the left eye to the hyperpigmented lesions were more in number and size in the peripheral retina|
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The patient's siblings, as well as parents, were also subjected to an extensive fundus examination. However no such retinal findings were detected in them.
There was really no doubt in the diagnosis, however this being such an unique case we decided to subject the patient to some more tests like a fundus fluorescein angiography (FFA), an optical coherence tomography (OCT), an ultrasound b scan (USG B scan) as well as a detailed visual field analysis, for which she was also given an appointment for the very next day. However, she did report back and was finally lost to follow-up.
| Discussion|| |
Bear track dystrophy is a rare condition forming part of the disorder known as the grouped CHRPE. These "bear tracks" are segmentally oriented, clearly demarcated, flat, hyper pigmented retinal lesions, often resembling animal footprints and hence the term. The lesions occur in one or both eyes, generally originate as small dots at the optic disc and gradually become more numerous and larger in the peripheral retina. This disorder is usually without any functional consequence with patients typically having a normal vision, color vision, normal visual fields, dark adaptation, electroretinography, and electrooculography findings.,,
A variant of this disorder, known as congenital grouped albinotic spots (CGAS), or "polar bear tracks", also exists, wherein the retinal pigment epithelium (RPE) is characterized by numerous, variably-sized, sharply circumscribed, placoid, white lesions organized in patterns.
There have also been reports in literature of a combination of both pigmented and non-pigmented lesions occurring in the same individual with grouped CHRPE.
CHRPE was first recognized by Mauthner in 1868, and reported on by Jacobi, that very year.
As a rule, these spots are not associated with any other fundus changes or any disease in the other parts of the eye.
Earlier it was believed that this condition was associated with familial adenomatous polyposis (FAP), Gardner syndrome, or intestinal cancer. However subsequent studies have proved that CHRPE is a benign condition and differs clinically from pigmented ocular fundus lesions (POFLs) seen with FAP, and that these patients, as well as their relatives, are not at any greater risk of developing intestinal cancer., FAP is an autosomal-dominant disease, characterized by thousands of adenomatous colonic polyps and a 100% lifetime risk of adenocarcinoma. POFL's associated with FAP, are RPE abnormalities occurring bilaterally in various shapes and sizes. These lesions may present as small, round, dark pigmentary changes around the vortex veins or as large as, upto 4.5 mm, ovoid pigmentary changes near the posterior pole. They may also show depigmentation in a lacunar or tail-like fashion along with peripheral RPE stippling and smaller, dark midperipheral lesions. Histologically hypertrophic and hyperplastic RPE abnormalities are seen, in addition to the hamartomatous and adenomatous changes.
Studies have also shown that patients with CHRPE are usually asymptomatic having a normal visual acuity, visual fields, colour examination, dark adaptation, and electrophysiologic findings and are generally detected during a routine examination.,, Similarly our patient too had no detectable ocular pathology. This rare, benign, lesion is also known to generally occur sporadically as was the case in our patient; however there have been some extremely rare cases of familial CHRPE reported in literature., In such cases an autosomal dominant pattern of inheritance with a variable expression has been suggested.
In our patient the number and size of the pigmentation gradually increased towards the periphery. Similar findings have also been noted in previous studies., Though in our case the lesions were present in both her eyes, however earlier studies have noted that in a majority of cases (84%) it is unilateral. Histological studies of the pigmented areas have shown retinal epithelial cells with hypertrophy and distinct irregularity in size and shape being arranged in one or two layers. The macula was not involved in our patient. Similar sparring of the macula has been seen in the previously reported cases of CHRPE.
Though, we did plan to investigate this patient further with a FFA, an OCT as well as an Usg B Scan, because the available literature mentions certain characteristic findings in these cases. However unfortunately she never reported back, perhaps because she did not have any visual complaints. With an FFA we expected to see decreased autofluorescence of the spots consistent with focal RPE atrophy as well as areas of increased autofluorescence suggesting RPE dysfunction, without any leakage. OCT in these cases usually shows a disruption in signal from the photoreceptor inner and outer segment junction along with an increased signal backscattering from the choroid in the area of the CHRPE. These lesions may also cause a progressive loss of photoreceptors in the overlying retina, which can be easily picked up by an OCT. Furthermore intraretinal extension of the RPE is a feature not seen in CHPRE and if detected on OCT may point towards the pigmented lesions of FAP. We even did plan for a B Scan ultrasonography, which in such cases typically reveals that RPE hypertrophy is flat to minimally elevated, normal or slightly hyper-reflective. A detailed visual field analysis was also planned, even though these cases are known to typically have normal visual fields because literature also mentions that field analysis of these patients may show relative or absolute scotomata.
| Conclusion|| |
The take home message is the differential diagnosis of CHRPE, which includes choroidal nevus, choroidal melanoma, chorioretinal scar, subretinal haematoma, pigmented epiretinal membrane and reactive retinal pigment epithelial hyperplasia.
Since CHRPE, in itself is a relatively benign condition, it becomes that much more important to distinguish it from the more serious vision/life threatening conditions like choroidal melanoma as well as from the POFL's associated with familial cancer syndromes like FAP.
It is also essential to ensure a regular long term follow-up in these cases even though 80% of these lesions show a very slow growth. Certain rare complications associated with these lesions have also been mentioned in literature like choroidal neovascular membrane on top of the CHRPE lesions, or the occasional formation of adenoma or adenocarcinoma which have limited growth potential and low tendency to metastasize and regular follow-up will ensure the early detection of these complications.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]