LRAT

The gene called LRAT carries instructions for making an enzyme named lecithin retinol acyltransferase. This enzyme works inside retinal cells and helps process vitamin A. Specifically, it converts one form of vitamin A (all-trans-retinol) into a stored form (a retinyl ester), which is an early step in what scientists call the visual cycle. The visual cycle continuously regenerates the light-sensitive pigment that the eye's 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.) cells need in order to detect light. When LRAT does not work properly, this recycling is disrupted and the retina cannot maintain normal light sensitivity. LRAT is one of several genes that act in the vitamin A pathway, and RPE65 is a closely related gene in the same pathway. LRAT-related retinal 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 it typically appears only when both inherited copies of the gene carry a change.

LRAT-related retinal disease usually begins early in life, often in childhood. The most common early symptom described is night blindness (nyctalopia), difficulty seeing in dim light. Other reported features include light-gazing behavior, sensitivity to light (photophobia), narrowing of the visual field, and reduced central vision. The gene is associated with Leber congenital amaurosis (also labeled LCA14) and with early-onset severe retinal dystrophy. It has also been linked to retinitis pigmentosa, a progressive loss of photoreceptors. The severity and course vary considerably from person to person. In a long-term follow-up of 13 people with LRAT changes, the disease appeared variable but was generally milder than the disease caused by RPE65 changes. In that group, some people progressed to low vision or blindness only in later decades of life, and small retinal white dots were seen in nearly half. More recently, LRAT changes have been reported to cause fundus albipunctatus, a milder condition marked by night blindness with relatively preserved daytime vision.

The role of the LRAT enzyme in vitamin A processing and the visual cycle is well understood. LRAT variants have been identified as a cause of retinal disease across multiple patient groups and countries. Detailed eye examinations have documented the clinical features of LRAT-related dystrophy in affected people. These features closely resemble those seen with RPE65 changes, which is expected because both genes act in the same vitamin A pathway. The natural history over many years has been described in a long-term follow-up study.

Because LRAT is a rare cause of inherited retinal disease, relatively few patients have been studied, which limits how confidently outcomes can be predicted. The full range of presentations is still expanding, as shown by newly reported variants and the recent link to fundus albipunctatus. How a specific LRAT change translates into severity, age of onset, or rate of progression cannot be reliably predicted for an individual. A rare dominantly inherited form linked to a large chromosomal rearrangement near LRAT has been reported in a single family, but this is unusual and separate from the typical recessive pattern.

As of this review, there is no approved treatment that specifically targets LRAT. An oral synthetic form of vitamin A called QLT091001 (9-cis-retinyl acetate) was tested in an open-label early-phase study of 14 people who had Leber congenital amaurosis from RPE65 or LRAT changes. In that study, most participants showed some improvement in vision, and the treatment was generally well tolerated, but most returned toward their starting vision after about two years. This type of medication, known as a visual cycle modulator, remains under investigation rather than being an established therapy. Separately, a gene replacement approach delivering a healthy LRAT gene improved retinal structure and light responses in a rat model of LRAT-associated retinitis pigmentosa, providing early proof of concept but not a human treatment.

• Oral vitamin-A-based therapy trial for RPE65 or LRAT disease

  Clinical trial (early-phase, open-label, no control group)

  What was found:

  Most participants had measurable improvement in visual field and some in visual acuity, effects were largely temporary, and no serious side effects occurred.

  Why it matters:

  It showed that replacing the missing visual-cycle building block could temporarily improve vision in some people with these gene changes.

  Limitation: Small, uncontrolled study combining two genes, with benefits that mostly faded within two years.

• Gene replacement therapy in an LRAT rat model

  Preclinical animal study

  What was found:

  Treated eyes showed improved retinal structure, stronger electrical responses to light, and better functional vision than untreated eyes.

  Why it matters:

  It offers early proof of concept that gene replacement might one day help LRAT-related retinitis pigmentosa.

  Limitation: Performed only in rats; this is not a treatment available to people.

• Long-term natural history of LRAT-related retinal disease

  Observational human cohort (retrospective natural history)

  What was found:

  First symptoms usually began in the first decade of life, phenotypes were variable, and disease was generally milder than that caused by RPE65 changes, with some people reaching low vision or blindness only in later decades.

  Why it matters:

  Understanding the slower course helps define the window during which future treatments might be most useful.

  Limitation: Small number of patients, many sharing the same variant, which limits how broadly the findings apply.

• Detailed phenotyping of early-onset LRAT dystrophy

  Human case series with detailed clinical characterization

  What was found:

  Four people had LRAT changes and showed severe, progressive childhood-onset disease with night blindness, field constriction, and light sensitivity, closely resembling RPE65-related disease.

  Why it matters:

  The similarity to RPE65 disease suggested LRAT deficiency might respond to therapies aimed at the vitamin A pathway.

  Limitation: Very few patients carried LRAT changes, so conclusions rest on a small sample.

• Expanding the LRAT phenotype to fundus albipunctatus

  Human case series (two patients)

  What was found:

  Both carried the same two LRAT variants, linking LRAT to this milder condition in addition to its established roles in more severe retinal disease.

  Why it matters:

  It shows LRAT changes can produce a broader and sometimes milder range of presentations than previously recognized.

  Limitation: Only two patients, so the finding needs confirmation in larger studies.

LRAT-related disease often begins in early childhood, so families may notice difficulty seeing in dim light or sensitivity to bright light in a young child. Because inheritance is usually 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.), siblings of an affected child can be carriers or affected, and carrier testing and genetic counseling may be useful for relatives considering their own family planning.

• Does my specific LRAT result match the recessive pattern usually seen, and what does that mean for my diagnosis?
• Based on my eye examination, does my presentation look more like Leber congenital amaurosis, retinitis pigmentosa, or a milder form such as fundus albipunctatus?
• How much functioning photoreceptor tissue remains, and how might that affect future options?
• What schedule of monitoring do you recommend for my vision over time?
• Would genetic counseling or carrier testing be helpful for my relatives?
• Are there any current studies relevant to LRAT that I could learn more about?

Confirming an LRAT result through genetic testing and speaking with a genetic counselor can help clarify what the finding means for you and your family. A retinal specialist can discuss the expected features and monitoring based on your own examination findings. If you are interested in research, RP Hope's Clinical Trials Finder can help screen for studies with LRAT preselected. RP Hope's guided pathway and patient stories may also help you plan next steps.