LCA5

The LCA5 gene, located on chromosome 6, carries the instructions for a protein called lebercilin. Lebercilin is found in the connecting cilium of photoreceptors — a slender bridge inside light-sensing cells through which proteins and building materials are shuttled to the part of the cell that detects light. Because of this role, LCA5-related disease is described as a retinal "ciliopathy (definition: A disease caused by a problem with cilia — tiny hair-like structures on cells, including the light-sensing cells in the retina, that the cell needs to work properly.)," a condition arising from problems in cilia function. Laboratory studies indicate that lebercilin works alongside other transport proteins to help form and maintain the photoreceptor (definition: A light-sensing cell in the retina. Rods (used for night and peripheral vision) and cones (used for color and detail) are the two types.) outer segment. LCA5-associated disease is inherited in an autosomal recessive (definition: An inheritance pattern where a person needs an altered copy of a gene from both parents to be affected. Parents with only one copy are usually unaffected carriers.) pattern, meaning a person is typically affected only when both copies of the gene carry disease-causing variants. Most reported LCA5 variants are "truncating" changes that are predicted to leave little or no working protein.

In study participants, LCA5-associated disease has usually caused a severe, early-onset loss of vision. Researchers have reported features such as nystagmus (involuntary eye movements), night blindness, and progressive loss of visual acuity and visual field. In one Spanish case series, individuals carrying LCA5 variants progressed toward blindness by around the third decade of life, with retinal changes resembling pigmentary retinopathy and atrophic macular lesions. Detailed imaging studies of a small number of patients have shown severe retinal disorganization but sometimes with islands of surviving photoreceptors, most often near the center of the retina and, in at least one report, in the mid-peripheral and peripheral retina. Although LCA5 changes most often cause LCA, the reported spectrum is broader: some families have had a milder, early-onset retinitis pigmentosa, and one report described two siblings with cone dystrophy. Importantly, this variability means that not everyone with LCA5 variants will have the same diagnosis, age of onset, or rate of progression, and an individual's outlook can only be assessed by their own clinical team.

It is well established that biallelic disease-causing variants in LCA5 lead to severe early-onset retinal degeneration, most commonly diagnosed as LCA. This has been confirmed across multiple independent cohorts from different countries, including Spain, Chile, Pakistan, India, Poland, Germany, Israel, and Palestine. It is also well documented that LCA5 is an uncommon cause of LCA — studies have estimated it accounts for roughly 2% of cases, though it was more frequent in a Spanish cohort, accounting for about 7.6%. It became a leading cause in populations with high rates of consanguinity such as a Chilean cohort. Laboratory and animal research consistently shows that loss of lebercilin disrupts the transport of proteins to the photoreceptor (definition: A light-sensing cell in the retina. Rods (used for night and peripheral vision) and cones (used for color and detail) are the two types.) outer segment, helping to explain why these cells degenerate.

Several things remain uncertain. The full range of vision outcomes is still being defined, and researchers note phenotypic variability both between and within genetic subgroups — including rare milder presentations and the recently reported association with cone dystrophy. How much functioning retina remains at different ages, and whether islands of surviving photoreceptors persist long enough to be targeted by treatment, appear to vary from person to person and are still being studied in small numbers of patients. Because LCA5 disease is rare, much of the detailed evidence comes from small case series and single-family reports, which limits how confidently general predictions can be made. The long-term outcomes of experimental gene therapy (definition: A treatment that delivers a working copy of a gene into cells to take over for a copy that isn't functioning properly.) beyond the first year, and whether benefit extends to people with milder disease, are not yet known.

RP Hope's reviewed records do not currently identify an approved, gene-specific medicine for LCA5-associated retinal disease. However, LCA5 is an active area of therapeutic research. A phase 1b/2a clinical trial tested a gene therapy (definition: A treatment that delivers a working copy of a gene into cells to take over for a copy that isn't functioning properly.), OPGx-001, which aims to deliver a healthy copy of the human LCA5 gene into the retina by subretinal injection. In three adults, researchers reported no serious treatment-related adverse events and measurable improvements in cone-mediated vision that persisted for at least 12 months in these severely affected patients. This is an early-stage safety and preliminary-efficacy study in a very small number of people. This therapy is not an approved or widely available treatment. Supporting laboratory and animal research — including gene augmentation in mice and patient-derived cells, and experiments in zebrafish and human retinal organoids — has helped clarify how loss of lebercilin damages photoreceptors and has explored gene-replacement and small-molecule strategies. These preclinical (definition: Research done in cells or animals, before a treatment is considered ready to be studied in people.) findings are promising for understanding the disease but are not treatments available to patients.

• First-in-human LCA5 gene therapy: one-year phase 1/2 results

  Early-phase clinical trial (safety and preliminary efficacy)

  What was found:

  There were no serious adverse events related to the therapy or procedure. Improvements in cone-mediated vision (averaging about a 1 log unit change on light-sensitivity testing) were detectable at 1 month and persisted for at least 12 months, along with better performance on a mobility test.

  Why it matters:

  It is the first published human evidence that gene replacement may improve some visual function in this severe condition and supports careful further study.

  Limitation: Only three severely affected adults were treated in one eye; this is very small, early-stage, and does not establish long-term safety, effectiveness, or availability.

• Gene augmentation in animal and cellular models of LCA5

  Preclinical animal and laboratory research

  What was found:

  Treatment partially restored retinal structure and visual responses in some treated mouse eyes and restored lebercilin protein and normal cilia numbers in the cellular model.

  Why it matters:

  These results provided the scientific rationale for moving toward human gene therapy studies for LCA5.

  Limitation: Findings in mice and cells do not guarantee the same benefit or safety in people and are not a treatment.

• LCA5 variants and the vision they cause in a Spanish cohort

  Observational human case series with clinical characterization

  What was found:

  LCA5 variants were found in about 7.6% of the LCA families (but none of the early-onset RP families). Affected individuals had nystagmus, night blindness, and progressive loss of acuity and visual field leading to blindness toward the third decade, with pigmentary retinopathy and atrophic macular changes.

  Why it matters:

  It provides one of the clearer pictures of how LCA5-related vision loss can progress and shows population differences in how common the gene is.

  Limitation: Findings come from a small number of families in one population and may not predict any individual's course.

• Large screening study defining the LCA5 mutation and phenotype spectrum

  Observational human genetic and phenotype study

  What was found:

  LCA5 variants explained about 2% of disease in this cohort; most were protein-truncating and associated with severe LCA, but two families had a milder early-onset RP. Some patients retained foveal photoreceptor structures and measurable vision.

  Why it matters:

  It establishes that LCA5 is a rare cause of retinal disease and shows the phenotype can range from very severe to somewhat milder, which is relevant to future treatment.

  Limitation: Genotype–phenotype links rested on small subsets, and imaging was available only for selected patients.

• Preserved peripheral photoreceptors in an LCA5 patient

  Single-patient case report

  What was found:

  Unusually large areas of relatively preserved photoreceptors were documented in the mid-peripheral and peripheral retina, beyond the small central island typically expected.

  Why it matters:

  Surviving photoreceptors are the target for gene therapy, so identifying where they remain could guide where treatment is delivered.

  Limitation: A single case cannot show how common this preservation is or how it changes with age.

Because LCA5-associated disease is inherited in an autosomal recessive (definition: An inheritance pattern where a person needs an altered copy of a gene from both parents to be affected. Parents with only one copy are usually unaffected carriers.) pattern, questions often arise about other family members. A genetic counselor can help relatives understand their own questions about carrier status and family planning. When supporting someone with vision loss, a helpful starting point is simply asking what kind of assistance they prefer rather than assuming, so their independence and autonomy are respected. Low-vision rehabilitation, accessible technology, and support with transportation, school, or workplace accommodations can all be useful to explore based on the person's own goals. Emotional and community support matters too — reading first-person accounts from others navigating a retinal diagnosis can be encouraging for both patients and families.

• Do my specific LCA5 variants explain my (or my child's) diagnosis, and are they considered clearly disease-causing?
• Based on my imaging and examinations, how much functioning retina appears to be preserved?
• What is the most accurate diagnosis for my situation — LCA, early-onset retinitis pigmentosa, or another pattern?
• How might my vision be monitored over time, and how often?
• Are there LCA5-specific research studies or gene therapy trials that I could learn more about?
• What low-vision or rehabilitation resources would you recommend for my current needs?

A confirmed genetic result can be valuable for understanding a diagnosis, informing family planning conversations, and identifying research opportunities. Genetic counseling can help explain what an LCA5 result means for you and your relatives and confirm that the variants identified are considered disease-causing. Because inherited retinal conditions vary widely, discussing your specific findings and imaging results with a retinal specialist is the best way to understand your own situation. RP Hope's genetic testing resource explains why testing matters and what questions to ask, and the My RP Pathway guide can help you find relevant support at any stage.