Collaborative Case #007: Cracked Egg
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Case Presentation
A 35-year-old Hispanic female presented for a macular issue. She described her vision as being “not perfect” with glasses since she was a teenager. Her medical and ocular history was unremarkable, and she was not taking any medications. BCVA OD was 20/25 and BCVA OS was 20/30. Extraocular motilities were full OD/OS, confrontation visual fields were full to finger counting and pupils were equal, round and reactive to light OD/OS. Her slit-lamp examination was unremarkable OU. Eye pressures were 12 mm Hg OU. On posterior segment evaluation she had normal optic nerves, normal vessels caliber and normal periphery (Figure 1).
Although all answers are acceptable, not all practices have FA in office and, depending on your scope of practice, you may not be able to perform this test. OCT and FAF are commonly available and are quick, noninvasive procedures that can provide valuable data to the practitioner. In addition, using FA will not necessarily confirm the diagnosis, but can confirm the presence or absence of a choroidal neovascular membrane (CNVM). Our patient's FA revealed bilateral central cystic hyperfluorescence without CNVM leakage. FAF revealed hyperfluorescence ring and incomplete parafoveal blockage (Figure 2).
OCT (Figure 3) reveled bilateral neurosensory detachment with hyperreflective material on the photoreceptor integrity line and underlying aspect of the neurosensory detachment. FAF reveled bilateral macular hyper-autofluorescent material inferiorly with small spots of increased autofluorescent superiorly and a hyper-autofluorescent ring.
Diagnosing other cases may not be as simple. Best disease can be easily confused with a variety of macular anomalies, including adult-onset vitelliform dystrophy (AVMD), AMD, and CSCR. These three conditions can cause central visual disturbance, macular cystic lesions, and macular lipofuscin-like deposits. As a result, distinguishing between them can be complex. One key factor that can help rule out other differentials is to ask when symptoms started.
Best disease occurs at childhood or early adulthood, whereas AVMD occurs in middle age or older. Another aspect that can help the doctor is the fact that macular dystrophies are bilateral and symmetrical, with no associations with other systemic conditions. CSCR is usually unilateral and manifests because of an increase in capillary choroidal permeability either due to high levels of stress (type A personality), pregnancy, or steroid use.
When ruling out differential diagnoses, OCT can be a valuable tool. The characteristic findings on OCT vary in different stages of the disease. In the vitelliform stage, OCT shows a homogeneous hyperreflective material. In the pseudohypopyon stage, due to gravity, the lipofuscin descends inferiorly, the vertical OCT reveals a clear fluid superiorly, and a hyper-reflective material inferiorly. In the atrophic stage, OCT reveals atrophy and loss of outer retinal layers, which resembles geographic atrophy from AMD.
Our patient underwent genetic testing, which revealed a positive mutation in the BEST1 gene. Hence, EOG was not a necessity. EOG measures the resting potential of the retinal pigment epithelium (RPE) in response to dark and light phases. A normal Arden ratio (light/dark ratio) is ≥ 1.8. In patients with Best disease, an Arden ratio < 1.5 is diagnostic. ERG evaluates the electrical function of the retina, including the photoreceptors, bipolar, and ganglion cells. Because Best disease is primarily an RPE dysfunction entity, the use of ERG is not a useful diagnostic. On the other hand, ERG is a valuable tool in evaluating other forms of retinal hereditary diseases that affect the outer retinal function, such as retinitis pigmentosa.
Introduction
Best disease is an autosomal dominant macular dystrophy in which there is a buildup of lipofuscin material in the RPE. This buildup is toxic to the cells and results in damage to the photoreceptors. Symptoms usually occur in childhood and patients with this disease are predominantly hyperopic, as was our patient. There are five stages to the disease:
1. The previtelliform stage presents with a normal fundus, yet the Arden ratio is reduced.
2. The vitelliform stage is when the classic bilateral egg yoke appearance is present
3. The pseudohypopyon stage occurs once the lipofuscin material accumulates inferiorly.
4. The vitelleruptive stage gives a “scrambled egg” appearance due to lipofuscin breakup and damage to the surrounding cells. Our patient presented to us at this stage
5. The atrophic stage is classified by loss of outer retinal layers, associated with macular scar, and/or the presence of CNVM.
With the help of OCT and FAF, we were able to confirm the vitelleruptive stage. There is no real cure for the disease. Patients with Best disease require close monitoring, given the possibility of CNVM development, which can be treated with anti-VEGF injections. In cases where vision is severely impaired, low vision rehabilitation can be highly advantageous. Because it is an autosomal dominant disease, we need to consult these patients about the condition, especially if they have children or are planning to have kids. A dilated fundus exam, electro-diagnostic testing, and genetic analysis are all essential in evaluating family members. We suggested that the patient's 5-year-old son undergo an examination as well.
His BCVA were 20/50 OU, he was a 4.00 D hyperope, and all of his preliminary testing and his slit-lamp examination were normal. As suspected, he too has Best disease (Figure 4). Utilizing OCT, (Figure 4) we were able to confirm that he was at the vitelliruptive stage.
Takeaway Points
- Always consider a diagnosis of inherited maculopathies in patients with longstanding macula symmetrical changes.
- Although the “egg yolk” lesion is the classic representation of Best disease, there are variable findings in association with progression/staging of the disease.
- EOG, genetic testing, and auxiliary tests all help in confirming the diagnosis.
Final Comment
In patients with long-standing, bilateral, symmetrical macular changes, always consider inherited maculopathies. Even though the classic presentation of Best disease is the bilateral “egg yolk” appearance, we need to keep in mind that the disease goes through stages and can present similarly to other conditions such as AVMD, CSCR and AMD. Ancillary testing, such as OCT, FAF, and FA, can have an important role in ruling out these etiologies.
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ABOUT THIS SERIES
On the path from initial diagnosis to severe disease management, patients may encounter a number of eye care providers. The Collaborative Care Case Series was developed, with guidance from William Trattler, MD, and Diana Shechtman, OD, FAAO, to challenge clinicians' understanding of diagnostic and treatment conventions and advance knowledge of all eye care providers along the continuum.
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