Autoimmune retinopathy
Rare autoimmune disease causing retinal degeneration and vision loss.
Autoimmune retinopathy is a rare disorder where the immune system mistakenly attacks retinal proteins, causing vision loss, blind spots, and visual field issues. Its exact cause is unclear, but it may stem from cancer or chemotherapy. The condition has two main forms: paraneoplastic (PAIR) and non-paraneoplastic (nPAIR), with the latter including cancer-associated retinopathy and melanoma-associated retinopathy.
Quick Facts
- Specialty
- Immunology Ophthalmology
Facts from the source article.
Pathophysiology
Autoimmune retinopathy (AIR) is thought to be driven by antiretinal antibodies that attack the eye's own proteins. A key mechanism is molecular mimicry, where the immune system mistakes a self-protein for a foreign one due to a similar sequence. In non-paraneoplastic AIR, this mimicry happens between retinal proteins and those from viruses or bacteria; in paraneoplastic AIR, it involves tumor antigens. The most common antibodies in cancer-associated retinopathy (CAR) target recoverin, while in non-paraneoplastic AIR they target alpha-enolase. Different AIR subtypes damage specific retinal cells: CAR and non-paraneoplastic AIR affect both rods and cones, whereas melanoma-associated retinopathy (MAR) only affects rods. Cone damage causes light sensitivity, color vision loss, and poor sharpness; rod damage leads to tunnel vision and slow dark adaptation.
Immunology and Autoimmunity
In autoimmune retinopathy, the immune system attacks the body's own retinal tissue. Both innate and adaptive immunity contribute to the disease. The innate immune response is triggered when damage-associated molecular patterns (DAMPs) released by damaged retinal cells are detected by pattern recognition receptors (PRRs) on macrophages and dendritic cells. These activated cells release pro-inflammatory cytokines, promoting inflammation and tissue damage. Specialized retinal macrophages (microglia) become activated, releasing inflammatory factors and presenting antigens to adaptive immune cells, bridging innate and adaptive responses. The adaptive immune system, involving T cells and B cells, is also important in AIR pathogenesis. While the innate response is critical for early detection and inflammation, it also amplifies the autoimmune process, leading to progressive retinal damage and vision loss.
Diagnosis
Diagnosing AIR is difficult due to symptom overlap with other disorders, and there is no standardized protocol, leading to underdiagnosis or misdiagnosis as retinitis pigmentosa (RP). Fundus examination may show narrowing of blood vessels, abnormal optic disc colouration, or retinal atrophy, but these findings are not indicative of AIR and only initiate the diagnostic process. An electroretinogram (ERG) is used to detect AIR; abnormal light and dark adaptation responses indicate the condition. ERG can also differentiate between CAR and MAR: cone responses suggest CAR, while a significant decrease in b-wave amplitude suggests MAR. Confirmation requires analysis for anti-retinal antibodies via Western blotting, immunohistochemistry (IHC), or ELISA. A family history of autoimmune disease can support a tentative diagnosis. Although typical in patients over 60, AIR can present in younger individuals, especially those with nPAIR. AIR and RP share symptoms like progressive vision loss and night blindness, but AIR is acquired, progresses faster, and may involve photophobia and color vision loss, often with a history of cancer or systemic inflammation.
Treatment
Treating autoimmune retinopathy is difficult because there is no standard therapy. Doctors focus on calming the immune system to stop further retinal damage. Options include intravenous immunoglobulin, plasmapheresis, and corticosteroids. When cancer is present, treatment targets the tumor through removal, chemotherapy, or radiation. Without cancer, therapy is more experimental, often using corticosteroids. A dexamethasone implant injected into the eye is being tested in trials and appears promising. The aim is to slow vision loss, not fix existing damage. IVIG is given over five days at 0.4 grams per kilogram daily. The donated antibodies block harmful antibodies from attaching to retinal proteins. Plasmapheresis filters the blood, removing problematic antibodies before returning the blood cells and plasma. How well a patient responds depends on how much retinal harm has already occurred.
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