What Is Bietti Crystalline Dystrophy?
Bietti crystalline dystrophy (BCD) is a degenerative ocular disorder with yellowish-white lipids (fats) deposition inside the eye's retina and cornea. Progression of the disease further results in impaired visual acuity. It was first noted by an Italian ophthalmologist Dr. G. B. Bietti, in 1937.
Is BCD a Common Disease?
Bietti crystalline dystrophy is a rare condition mainly affecting teenagers and young adults. However, some also acquire the disease in their third decade.
Can BCD Be Inhertited?
Bietti crystalline dystrophy runs in families and shows an autosomal recessive inheritance pattern. However, many people remain carriers of the condition; hence, screening such at-risk patients is necessary.
What Are the Risk Factors Associated With BCD?
Certain risk factors can aggravate Bietti crystalline dystrophy; one of the significant risk factors is the patient's ethnicity. The Asian population, especially Chinese people, is more susceptible to BCD. Approximately 10 percent of patients with retinitis pigmentosa are reported to be suffering from BCD.
How Is BCD Acquired?
The exact mechanism involved in BCD is unclear. Genetic mutation of the CYP4V2 is the state's leading cause. The CYP4V2 gene is involved in the metabolism of lipids and steroids. Therefore, the dysfunction in lipid metabolism is hypothesized to be the chief source of BCD.
What Are the Clinical Signs and Symptoms of the Condition?
The classic clinical feature of Bietti crystalline dystrophy is the presence of yellowish-white glistening crystals of lipids in the retinal region of the eye with or without involving the cornea. About 25 to 33 percent of the cases affect the cornea. If the cornea is concerned, the crystals are most likely present in the anterior stroma of the cornea. Other presentations of BCD are:
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Reduced visual acuity.
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Nyctalopia or night blindness (inability of a person to view objects in dim light).
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Blindness.
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Asymmetry of the eyes.
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Patchy hyperfluorescent areas of the retinal pigment epithelium are seen using fluorescent angiography.
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The deposition of the lipid is more restricted to the corneal limbus.
How Is Bietti Crystalline Dystrophy Diagnosed?
Bietti crystalline dystrophy is usually diagnosed clinically. The diagnostic tools which are employed to confirm the clinical diagnosis of the condition are:
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Electroretinography. The retina's electroretinography helps evaluate the dysfunction of the rods and cones of the retina.
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Multifocal electroretinography helps in determining sectional areas of abnormal areas of dysfunction.
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Spectral-domain optical coherence tomography is used to evaluate and identify the reflective dots.
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Optical coherence tomography (OCT) shows hyperreflective dots (crystalline deposits) in the choriocapillaris region. The degeneration is seen as more prevalent in the outer retinal layer.
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Molecular gene testing. Both single and multi-gene testing methods are performed to diagnose the gene responsible for the genetic abnormality.
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Fundus autofluorescence is performed to detect the extent of the lesion and the disease's progression over time.
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Visual defects are tested with the help of Humphrey's visual field tests.
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In vivo confocal microscopy.
How Are Patients With Bietti Crystalline Dystrophy Treated?
There is no specific treatment for BCD. However, patients with Bietti crystalline dystrophy are kept under regular follow-up once a year to monitor for any deterioration of the vision. Ophthalmologists look for macular holes, edema, and choroidal neovascularization (formation of new blood vessels).
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Anti-vascular endothelial growth factors (anti-VEGF) are injected to treat choroidal neovascularization.
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Genetic counseling is beneficial for to-be parents with a family history of BCD during family planning.
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Patients with progressive vision loss are referred to ophthalmologists or low-vision specialists to cope with blindness. They prescribe low-vision aids or devices that help in optimizing vision.
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Eye care professionals must be trained to counsel patients with gradual loss of vision and help them in their employment, education, etc.
What Is the Role of Genetic Counseling in the Management of Patients With BCD?
Genetic counseling (the process of informing patients and families of the genetic inheritance of the disease or state). Genetic counseling involves risk assessment of the family members, detection of the carriers, family planning, and DNA (deoxyribonucleic acid) banking.
Genetic testing of the fetus prenatally helps determine the risk of the disease and the carrier status of the fetus. In addition, prenatal and preimplantation testing is done in mothers with an increased risk of Bietti crystalline dystrophy syndrome.
What Are the Complications of BCD?
Patients suffering from BCD suffer from gradual and progressive loss of visual acuity, ultimately leading to blindness.
Other complications of BCD are:
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Sclerosis of choroidal blood vessels.
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Retinal pigment epithelial pigment.
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Clumping of the pigment.
What Are the Conditions That Are Similar to BCD?
The conditions that are to be ruled out before forming a confirmative diagnosis of Bietti crystalline dystrophy are:
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Retinitis pigmentosa (a collection of retinal disorders that results in gradual loss of vision).
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Infectious-crystalline keratopathy (inflammation of the cornea due to a rare infection that results in branching opacities of the corneal stroma).
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Sjogren-Larsson syndrome (a dermal condition comprising dry, scaly skin and other eye problems).
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Toxicity due to consumption of drugs like Methoxyflurane, Tamoxifen, and Canthaxanthin.
What Is the Prognosis of the Condition?
Bietti crystalline dystrophy usually results in peripheral vision loss, with progressive visual acuity loss later in life.
Conclusion
Bietti crystalline dystrophy is a rare ocular condition described by the deposition of yellowish-white lipids in the retina and cornea of the eye. Genetic mutation of genes responsible for the metabolism of lipids is one of the major causes of BCD. Asians, especially Chinese, are more prone to get BCD. The disease is diagnosed during clinical evaluation, which appears as glistening crystalline deposits. Patients also suffer from night blindness and gradual loss of vision with time. The diagnosis of the condition is confirmed with the help of electroretinography.
There is no particular treatment for BCD; however, Anti-VEGF injections are given to patients with a history of CNV (choroidal neovascularization). Patients are monitored regularly to check for the deterioration of their eyesight. Genetic counseling and prenatal screening help earlier detect the carrier and at-risk patients. BCD is a degenerative disorder with no treatment and requires monitoring and counseling.
