|Year : 2021 | Volume
| Issue : 1 | Page : 65-68
Bietti's crystalline dystrophy
Adline Harris, CS Sandhya
Department of Ophthalmology, S.V Medical College, Tirupathi, Andhra Pradesh, India
|Date of Submission||16-Jul-2021|
|Date of Decision||10-Aug-2021|
|Date of Acceptance||15-Aug-2021|
|Date of Web Publication||01-Nov-2021|
Dr. Adline Harris
Department of Ophthalmology, S.V Medical College, Tirupati, Andhra Pradesh - 517507
Source of Support: None, Conflict of Interest: None
Bietti's crystalline dystrophy (BCD) is a relatively rare tapetoretinal degeneration with marginal corneal dystrophy characterized by subepithelial corneal crystals at the limbus and intraretinal crystals in the posterior pole with atrophy of the retinal pigment epithelium and choroidal sclerosis caused by a mutation in the CYP4V2 gene. In this article, we present a case of a middle-aged female with a history of gradual, progressive, painless diminution of vision in both eyes showing multiple diffuse yellowish crystalline structures in the fundus with atrophy of underlying structures. Spectral domain-ocular coherence tomography of macula revealed bilateral multiple hyperreflective dots with outer retinal tubulations. Electroretinogram showed subnormal scotopic and photopic responses. Although very few cases of BCD have been reported, a wide knowledge about the disease is necessary to diagnose early and hence to uplift the quality of life to the patient by providing low visual aids and visual rehabilitation.
Keywords: Bietti's, Bietti's dystrophy, corneal dystrophy, crystalline retinopathy, nyctalopia, tapetoretinal degeneration
|How to cite this article:|
Harris A, Sandhya C S. Bietti's crystalline dystrophy. J Ophthalmol Clin Res 2021;1:65-8
| Introduction|| |
Professor Gian Battista Bietti first reported Bietti's crystalline dystrophy (BCD) as tapetoretinal degeneration with subepithelial corneal deposits in the limbus and small crystalline spots in the posterior pole of the retina. BCD is an autosomal recessive inherited disease caused by mutations in CYP4V2 presenting between the second and fourth decades of their life with complaints of diminution of vision, progressive night blindness, defective color vision, constriction of visual fields, or maybe an incidental finding during ophthalmic evaluation. Here, we report a case of BCD in a patient who attended a tertiary health-care center in South India.
| Case Report|| |
A 35-year-old female, a known hypertensive individual, came to the ophthalmology department with complaints of gradual, progressive, painless diminution of vision for 3 years with a history of night blindness for 2 years. There was no history of consanguinity in her parents or history of similar complaints in any of her family members (parents, siblings, offspring). There was no history of any other drug usage except for antihypertensives.
The best-corrected visual acuity was 6/12 in the right eye and 6/18 in the left eye and her near vision was N6 in both eyes. On slit-lamp examination, anterior segment examination was normal in both eyes. Fundus examination showed a normal optic disc with bilateral multiple refringent dot-like structures with atrophy of underlying structures. Features suggestive of underlying retinitis pigmentosa were noted with arteriolar attenuation and scattered bony spicules [Figure 1], [Figure 2], [Figure 3]. Color vision was normal in both eyes.
|Figure 1: Fundus photograph showing normal optic disc with bilateral multiple diffuse yellowish crystalline dot-like structures (marked with arrows) with atrophy of underlying structures. Arteriolar attenuation was present with few bony spicules (marked with a star) indicating the presence of retinitis pigmentosa|
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Spectral domain-ocular coherence tomography (SD-OCT) of the macula of both eyes revealed multiple hyperreflective dots in inner layers of the retina, retinal pigment epithelium-Bruch's membrane complex, and choroid with outer retinal tubulations [Figure 4]. Electroretinogram (ERG) showed reduced scotopic and photopic responses in both eyes [Figure 5] and [Figure 6]. The patient was given low visual aids and was asked to follow up every 6 months to look for progression and to detect complications such as cystoid macular edema, choroidal neovascular membrane (CNVM), and macular hole formation at the earliest.
|Figure 4: Spectral domain-ocular coherence tomography of the macula of both eyes (a and b –right eye, c and d – left eye) showing multiple hyperreflective dots in the inner layers, retinal pigment epithelium–Bruch's membrane complex, and choroid with irregularity of inner layers and outer retinal tubulations (marked with arrows) in a and b|
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|Figure 5: Electroretinogram of the patient showing the reduced amplitude of b wave (rod response) in scotopic 0.01 and reduced amplitude of a and b wave (combined response) in scotopic 3.0 and 10.0 with decreased amplitude of oscillatory potentials – indicating reduced scotopic responses in both eyes|
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|Figure 6: Electroretinogram of the patient showing decreased amplitudes of the cone a-wave and 30 Hz flicker responses depicting reduced photopic responses in both eyes|
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| Discussion|| |
BCD is a relatively uncommon disease characterized by tapetoretinal degeneration with marginal corneal dystrophy. BCD is reported to have a higher prevalence in the East Asian population, especially in Chinese and Japanese people. The prevalence is about 10% in autosomal recessive RP patients and 3% in nonsyndromic RP patients. BCD is characterized by outer corneal crystals at the limbus and intraretinal crystals in the posterior pole. The mutated gene in BCD, CYP4V2 which is a member of the cytochrome p-450 family is responsible for the defective omega oxidation of ocular fatty acids. However, the exact mechanism by which there occurs crystalline deposition on the retina, cornea, circulating lymphocytes, and skin fibroblasts remains unclear.
BCD is a progressive disease presenting with nyctalopia, diminution of vision, and visual field defects in the second to the fourth decade of life. They may progress and end in blindness in the fifth or sixth decade of life.
The crystalline deposits in the cornea first appear in the inferior or superior limbus, which later spreads to 360° of the limbus. The corneal crystalline deposits may in due course of the disease disappear or may progress to corneal degeneration, keratopathy, or scar formation.
The classical fundus picture of BCD consists of multiple crystalline deposits in the posterior pole with degeneration of the retina and choroidal sclerosis. This may later disappear or progresses to chorioretinal atrophy with hyperpigmentation. In due course, it may resemble retinitis pigmentosa with attenuation of retinal vessels.
Visual field changes such as paracentral scotomas and peripheral field loss depending upon the severity of the disease may occur. SD-OCT may show crystals in different layers of the retina as tiny hyperreflective lesions. Studies have shown various spherical, tube formation, or rosette formation of these hyperreflective lesions in patients with BCD. SD-OCT is also helpful in the diagnosis of cystoid macular edema, CNVM, and macular hole formation in due course which are the potential complications of BCD.
The ERG finding in patients with BCD may vary from patients with normal ERG amplitude and latency having diminution of vision and nyctalopia to generalized rod-cone dysfunction. In general, ERG is subnormal with reduced amplitude in scotopic, photopic, and 30 Hz flicker responses. SD-OCT and ERG hence play a vital role in differentiating various crystalline retinopathies and aiding in the diagnosis of BCD.
Even though much has been studied about the presentation, the role of CYP4V2 in the pathogenesis, and diagnosis of this uncommon inherited disease, a promising treatment for this condition is yet to be achieved. Low visual aids, management of complications, and genetic counseling are practiced and gene therapy has a future role in the management of this disease.
Although very few cases of BCD have been reported in Indian literature, a wide knowledge about the disease is necessary to diagnose early so that the quality of life and vision can be improved by providing low vision aids and visual rehabilitation.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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