Dominant Drusen

Dominant Drusen, also known as Doyne honeycomb retinal dystrophy, is a rare, inherited eye condition that affects the retina, the light-sensitive tissue at the back of the eye. It is caused by a change (mutation) in a specific gene called EFEMP1, which is passed down through families. In this condition, small yellow deposits called drusen build up under the retina. Over time, these deposits can grow and group together, often forming a honeycomb-like pattern. In the early stages, usually in a person's 20s or 30s, there may be no symptoms at all. However, as the drusen accumulate, usually around the 40s or 50s, people may start to notice changes in their vision. These changes can include blurry or distorted vision, difficulty seeing in low light, and trouble with fine details like reading or recognizing faces. While central vision can become significantly impaired in later stages, peripheral (side) vision usually remains unaffected, allowing people to maintain a degree of independence. Currently, there is no cure for Dominant Drusen, but regular eye exams are crucial to monitor the condition and manage any complications. In some cases, abnormal blood vessels can grow under the retina, causing further vision loss; this can often be treated with specific eye injections. Using brighter lights, magnifying devices, and maintaining a healthy lifestyle can also help manage the symptoms and support overall eye health.

Condition category: Macular Dystrophy

Prevalence: Rare

Inheritance patterns: Autosomal Dominant

Age of onset: Typically 4th to 5th decade of life (30s to 40s), though patients may be asymptomatic initially.

Clinical overview: Note: Dominant Drusen (also known as Doyne Honeycomb Retinal Dystrophy) is now more commonly referred to as Malattia Leventinese. Both terms describe the same autosomal dominant macular dystrophy caused by EFEMP1 mutations. See also the Malattia Leventinese and Familial Drusen entries. Dominant Drusen, also known as Doyne Honeycomb Retinal Dystrophy (DHRD) or Malattia Leventinese (MLVT), is a rare, progressive, autosomal dominant inherited retinal dystrophy. It is characterized by the early-onset accumulation of yellowish deposits called drusen beneath the retinal pigment epithelium (RPE) in the macula and peripapillary regions. These deposits often form a distinct radial or honeycomb pattern. The condition shares significant clinical and pathological similarities with age-related macular degeneration (AMD), including drusen formation, RPE atrophy, and the risk of choroidal neovascularization (CNV). However, Dominant Drusen typically presents much earlier in life, usually in the fourth or fifth decade. The disease is caused by a specific mutation in the EFEMP1 gene, which encodes the fibulin-3 protein. Dominant Drusen is clinically significant as it serves as a monogenic model for studying the pathogenesis of drusen formation and macular degeneration. Understanding the molecular mechanisms underlying this condition provides valuable insights into the more common AMD. The condition is cataloged under OMIM #126600 (phenotype) and #601548 (gene), and Orphanet ORPHA:75376.

Patient and family guide: Dominant Drusen, also known as Doyne honeycomb retinal dystrophy, is a rare, inherited eye condition that affects the retina, the light-sensitive tissue at the back of the eye. It is caused by a change (mutation) in a specific gene called EFEMP1, which is passed down through families. In this condition, small yellow deposits called drusen build up under the retina. Over time, these deposits can grow and group together, often forming a honeycomb-like pattern. In the early stages, usually in a person's 20s or 30s, there may be no symptoms at all. However, as the drusen accumulate, usually around the 40s or 50s, people may start to notice changes in their vision. These changes can include blurry or distorted vision, difficulty seeing in low light, and trouble with fine details like reading or recognizing faces. While central vision can become significantly impaired in later stages, peripheral (side) vision usually remains unaffected, allowing people to maintain a degree of independence. Currently, there is no cure for Dominant Drusen, but regular eye exams are crucial to monitor the condition and manage any complications. In some cases, abnormal blood vessels can grow under the retina, causing further vision loss; this can often be treated with specific eye injections. Using brighter lights, magnifying devices, and maintaining a healthy lifestyle can also help manage the symptoms and support overall eye health.

Symptoms and clinical features: In the early stages of Dominant Drusen, patients are typically asymptomatic. Small drusen begin to accumulate in the macula and peripapillary areas, often in a radial distribution, but these do not initially affect visual function. This stage can last for years or even decades. During the intermediate stages, usually in the 4th or 5th decade of life, patients begin to experience insidious visual disturbances. Initial symptoms often include blurry vision, difficulty seeing in low light (nyctalopia), and trouble with fine details. As drusen enlarge and coalesce into the characteristic honeycomb pattern, patients may notice metamorphopsia (distortion of straight lines), photopsias (flashes of light), mild dyschromatopsia (color vision changes), and relative paracentral scotomas (blind spots). In advanced stages, typically in the 6th decade and beyond, central vision becomes significantly impaired. Visual acuity can deteriorate to 20/200 or worse due to geographic atrophy of the RPE and overlying photoreceptors. The development of secondary choroidal neovascularization (CNV) can cause sudden, severe vision loss, subretinal hemorrhage, and subsequent fibrovascular scarring. Despite severe central vision loss, peripheral vision is generally preserved.

Molecular pathology: The EFEMP1 gene encodes fibulin-3, an extracellular glycoprotein that is widely expressed in tissues, including the eye. Fibulin-3 is a critical component of the extracellular matrix, interacting with other proteins like ECM1 and TIMP-3 to maintain the integrity of basement membranes, such as Bruch's membrane in the retina. It plays a role in structural support and regulating cell signaling pathways, including the inhibition of angiogenesis. The pathogenic R345W mutation in EFEMP1 leads to protein misfolding and inefficient secretion. The mutant fibulin-3 accumulates within cells and in the extracellular space, specifically forming basal laminar deposits between the retinal pigment epithelium (RPE) and Bruch's membrane. These deposits are the precursors to the clinically visible drusen. The accumulation of mutant fibulin-3 and other proteins in these deposits disrupts the normal architecture and function of the RPE and Bruch's membrane. This disruption can lead to RPE cell ultrastructural alterations, complement activation, and decreased cholesterol efflux, ultimately resulting in RPE atrophy, photoreceptor loss, and the potential development of choroidal neovascularization.

Genetics: Dominant Drusen is inherited in an autosomal dominant pattern, meaning a single copy of the mutated gene is sufficient to cause the disorder. The condition is caused by mutations in the EFEMP1 gene, located on chromosome 2p16.1. The hallmark genetic cause is a highly specific hotspot missense mutation in exon 10 of the EFEMP1 gene, specifically an arginine-to-tryptophan substitution at codon 345 (Arg345Trp or R345W). This single recurrent mutation has been identified in patients diagnosed with both Doyne honeycomb retinal dystrophy and Malattia Leventinese, confirming they are phenotypic variants of the same genetic entity. There is significant phenotypic variability and genetic heterogeneity even among individuals with the same R345W mutation. Disease severity and progression can vary widely between eyes of the same patient and among affected family members, suggesting the potential influence of other genetic or environmental modifying factors.

Diagnostic evaluation: Diagnosis is based on clinical findings and confirmed by genetic testing. Fundoscopy reveals characteristic drusen deposition between the Bruch membrane and the RPE, typically in the macular and peripapillary regions, often forming a radial or honeycomb pattern. Pigmentary changes and signs of choroidal neovascularization (CNV) may also be observed. Optical coherence tomography (OCT) demonstrates hyperreflective deposits with elevation between the RPE and Bruch's membrane. In advanced stages, diffuse loss of the ellipsoid zone and outer/inner segment disruption can be seen. Fundus autofluorescence (FAF) shows hyper-autofluorescence corresponding to drusen and hypo-autofluorescence in areas of macular atrophy. Fluorescein angiography (FA) and OCT-Angiography (OCT-A) are crucial for detecting and characterizing secondary CNV. Electroretinography (ERG) may show low-normal scotopic and photopic responses initially, which can become sub-normal in severe disease. Genetic testing for the EFEMP1 gene, specifically the R345W mutation, serves as a confirmatory diagnostic tool. Differential diagnoses include age-related macular degeneration (AMD), early-onset drusen, Sorsby fundus dystrophy, pattern dystrophies, and Stargardt disease.

Differential diagnosis: Differential diagnosis of dominant drusen (Doyne honeycomb retinal dystrophy) includes: (1) Age-related macular degeneration — later onset, no autosomal dominant pattern, different drusen distribution. (2) Familial drusen (Malattia Leventinese) — same condition, EFEMP1 mutations. (3) Sorsby fundus dystrophy — subretinal deposits with early CNV, TIMP3 mutations. (4) Membranoproliferative glomerulonephritis type II — drusen with renal disease. (5) Cuticular drusen — small uniform drusen, stars-in-the-sky FA pattern, CFH association.

Natural history: The natural history of Dominant Drusen typically begins with an asymptomatic phase in early adulthood. Drusen begin to accumulate, but patients usually maintain good vision. Symptoms typically manifest in the 4th or 5th decade of life as the drusen enlarge, coalesce, and affect the macula. Disease progression is generally slow, with a gradual decline in central visual acuity. Structural retinal changes follow a pattern: well-defined pigment epithelial detachments (PEDs) coalesce, leading to loss of outer retinal lamination and subretinal fibrosis, followed by RPE atrophy. A significant prognostic factor is the development of choroidal neovascularization (CNV), which can occur in advanced stages. The presence of CNV is associated with a significantly worse natural history, rapid progression, and more severe vision loss. However, many patients maintain functional peripheral vision throughout their lives.

Management and treatment research: Currently, there is no cure for Dominant Drusen, and management is primarily supportive and observational. Regular ophthalmic monitoring with OCT and FAF is essential to track disease progression and detect complications early. Patients are advised to maintain a healthy lifestyle, including smoking cessation and a diet rich in leafy greens, and to use UV protection. Low vision aids and rehabilitation services are recommended as central vision declines. The most critical medical intervention is the treatment of secondary choroidal neovascularization (CNV). If CNV develops, it is typically managed with intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) agents, such as bevacizumab. These injections can effectively reduce subretinal fluid, stabilize or improve visual acuity, and prevent severe scarring. Historically, laser therapies (such as low-energy argon or sub-threshold nanolaser) have been explored to clear drusen deposits, with some reports of functional improvement, but these are not standard of care. Research into targeted therapies is ongoing. The SVT-001 trial (Sanaregan Vision Therapeutics) is an early-phase clinical study evaluating a regenerative cell therapy specifically for patients with familial drusen associated with EFEMP1 mutations. Other research focuses on understanding the complement pathways and lipid metabolism involved in drusen formation, which may lead to future pharmacological interventions or gene-editing approaches.

Outlook: The prognosis for Dominant Drusen is variable but generally involves a slow, progressive decline in central visual acuity. Most patients maintain functional vision for many years, and peripheral vision is typically spared, allowing for continued independence in many daily activities. The most significant factor negatively affecting prognosis is the development of choroidal neovascularization (CNV), which can lead to rapid and severe central vision loss if left untreated. Regular monitoring and prompt treatment of CNV are essential for preserving vision and maintaining quality of life. Low vision aids and supportive services can significantly help patients adapt to visual changes.

Epidemiology: Dominant Drusen is a rare condition with less than 100 reported cases worldwide. It was initially described in families from Oxford, England (Doyne honeycomb retinal dystrophy) and the Leventine valley in Switzerland (Malattia Leventinese). While it affects both sexes, some studies have noted an apparent sex imbalance with a higher prevalence in females (male-to-female ratio of 1:3.4 in one cohort), though this may be subject to selection bias.

Selected references: 1. Stone EM, et al. A single EFEMP1 mutation associated with both Malattia Leventinese and Doyne honeycomb retinal dystrophy. Nat Genet. 1999. PMID: 10369267 2. Michaelides M, et al. Maculopathy due to the R345W substitution in fibulin-3: distinct clinical features, disease variability, and extent of retinal dysfunction. Invest Ophthalmol Vis Sci. 2006. PMID: 16799056 3. Marmorstein LY, et al. Formation and progression of sub-retinal pigment epithelium deposits in Efemp1 mutation knock-in mice: a model for the early pathogenic course of macular degeneration. Hum Mol Genet. 2007. PMID: 17660533 4. Fu L, et al. The R345W mutation in EFEMP1 is pathogenic and causes AMD-like deposits in mice. Hum Mol Genet. 2007. PMID: 17728325 5. de Guimarães TAC, et al. A Long-Term Retrospective Natural History Study of EFEMP1-Associated Autosomal Dominant Drusen. Invest Ophthalmol Vis Sci. 2024. PMID: 38899960 6. Zhang Y, Marmorstein LY. Focus on Molecules: Fibulin-3 (EFEMP1). Exp Eye Res. 2010. PMID: 19799900