A systematic review of 70 patients with Danon disease reveals that eye changes often appear before any heart symptoms, giving ophthalmologists a critical window to identify this rare but serious genetic condition. In 16% of cases, retinal changes were the only initial sign of the disease, and in some patients, vision problems appeared years before a heart diagnosis .

What Is Danon Disease and Why Should Eye Doctors Care?

Danon disease is a rare inherited form of severe cardiomyopathy, a condition where the heart muscle becomes weakened and enlarged. Most people have never heard of it, and many eye doctors may not immediately recognize its ocular signs. However, a new systematic review published in the American Journal of Ophthalmology found that the eyes often tell the story first. Among 70 patients studied, aged 6 to 81 years, 81% showed retinal signs, making pigmentary retinopathy a potential early warning signal .

The significance of this finding cannot be overstated. Because Danon disease affects the heart, early detection through eye screening could lead to earlier genetic testing, cardiac evaluation, and coordinated care between ophthalmologists and cardiologists. This multidisciplinary approach may improve outcomes and prevent serious complications.

What Eye Changes Indicate Possible Danon Disease?

The retinal changes associated with Danon disease are distinctive but require careful examination to detect. Researchers identified several characteristic patterns that ophthalmologists should recognize :

• Peripheral pigmentary changes: Patients often develop "salt-and-pepper" pigmentary variation in the peripheral and mid-peripheral retina, a pattern that looks like scattered dark and light spots across the back of the eye.
• Macular involvement: About 62% of patients experienced changes in the macula, the central part of the retina responsible for detailed vision, most often showing non-specific retinal pigment epithelium (RPE) variations.
• Advanced retinal damage: In severe cases, 13% of patients developed macular atrophy, cystoid macular edema (fluid-filled cysts in the macula), or bull's-eye maculopathy, a distinctive circular pattern of damage.

Beyond what the eye doctor sees during a standard exam, advanced imaging reveals even more detail. Optical coherence tomography (OCT), a non-invasive imaging technique, showed retinal pigment epithelium and ellipsoid zone disorder in 85% of patients who underwent the test. Additionally, 61% displayed hyperreflectivity in the outer nuclear layer, and fundus autofluorescence imaging often revealed mottled patterns of increased and decreased fluorescence .

How Should Ophthalmologists Screen for Danon Disease?

The research team emphasized that detecting these subtle changes requires a comprehensive approach beyond a routine eye exam. Researchers noted that "ophthalmologists should consider Danon disease in the differential diagnosis of unexplained pigmentary retinopathy" . This means when an eye doctor encounters a patient with unexplained retinal pigmentation changes, Danon disease should be on the list of possible diagnoses.

To catch these changes early and monitor progression, the study recommends incorporating specific imaging techniques into ongoing care:

• Dilated fundoscopy: A thorough dilated eye exam allows the ophthalmologist to visualize the entire retina and identify peripheral pigmentary changes that might otherwise be missed.
• Fundus autofluorescence imaging: This specialized imaging technique uses natural fluorescence in the retina to reveal patterns of damage and degeneration that may not be visible during a standard exam.
• Macular OCT: Optical coherence tomography of the macula provides detailed cross-sectional images of retinal layers, allowing detection of subtle structural changes and progression over time.

The researchers stated that "our findings support incorporating dilated fundoscopy, fundus autofluorescence, and macular OCT into ongoing care to detect subtle or progressive retinal changes" . This comprehensive imaging approach is particularly important because some patients may have retinal changes that appear normal on clinical examination alone.

Why Early Detection Matters for Patients

The timing of diagnosis can be critical for Danon disease patients. The systematic review found that in 7 individuals, retinal problems occurred years before a systemic heart diagnosis. While heart issues could also appear first, the eye findings provide an opportunity for earlier intervention. With advances in genetic testing and cardiac therapies, regular retinal screenings become a gateway to comprehensive care .

Other ocular findings associated with Danon disease include myopia (nearsightedness) in 16% of patients, high myopia in 9%, and white dots or lens cortical opacities in 13%. These additional eye changes can serve as supporting clues for diagnosis .

The implications are clear: ophthalmologists are often the first healthcare providers to examine patients thoroughly, and they have the tools to detect early signs of systemic disease. By recognizing the ocular manifestations of Danon disease and performing appropriate imaging, eye doctors can facilitate earlier genetic testing and coordinate care with cardiologists, potentially improving outcomes for patients with this rare but serious condition.