Bilateral Acute Retinal Necrosis Complicated by Concurrent Neuroborreliosis in an Immunocompromised Patient: A Case Report

The human eye is a delicate organ, protected by layers of defense that usually keep infections at bay. However, when the body's immune system is weakened, either by disease or by medication used to treat other conditions, these defenses can fail, allowing viruses and bacteria to invade the eye. One such dangerous infection is acute retinal necrosis, a condition where a virus attacks the light-sensitive tissue at the back of the eye, causing it to die and leading to severe vision loss. This process is often driven by the varicella-zoster virus, the same germ that causes chickenpox and shingles. In rare and complex cases, doctors must determine if a single virus is the sole culprit or if multiple infections are working together to cause the damage. Understanding these interactions is vital, because treating the wrong infection or missing a second one can mean the difference between saving sight and losing it.

A recent report from Sankt Erik Eye Hospital details a challenging case involving a fifty-year-old woman whose vision began to fail in a way that defied standard treatment. The patient had a history of rheumatoid arthritis, an autoimmune condition she managed with a medication called sulfasalazine, and an abdominal tumor. While taking this medication, she began to suffer from a persistent headache and fatigue that lasted for three weeks. When she finally developed pain and blurred vision in her left eye, doctors initially diagnosed her with bilateral acute retinal necrosis, a condition affecting both eyes, and confirmed the presence of the varicella-zoster virus in the fluid inside her left eye. They immediately started her on high doses of an antiviral drug called valacyclovir and added a steroid to reduce inflammation.

Despite this aggressive treatment, the patient's condition did not improve as expected. While the left eye, which had been surgically drained to test the fluid, began to stabilize, her right eye grew worse. The inflammation inside the right eye increased, and her headache intensified. This paradoxical response—where one eye improved while the other deteriorated despite identical treatment—signaled to the medical team that something else was happening. They realized that the virus alone might not be the whole story. The doctors performed a comprehensive search for other hidden infections, including scanning her brain and taking a sample of the fluid surrounding her spinal cord.

The investigation revealed a second, previously undiagnosed infection. The fluid around her brain and spinal cord showed strong evidence of neuroborreliosis, an infection caused by the bacteria Borrelia burgdorferi, which is typically transmitted by tick bites. The patient recalled being bitten by a tick about a year earlier. The medical team concluded that her weakened immune system, caused by both her arthritis medication and the lingering effects of the bacterial infection, had allowed the virus to reactivate and spread to both eyes. The bacterial infection was likely suppressing her immune response in a way that made the viral infection harder to control. Once the doctors added targeted antibiotics to treat the bacterial infection, the situation changed rapidly. The inflammation in her right eye cleared up, her vision improved significantly, and the spread of the retinal damage stopped in both eyes.

Although the treatment successfully halted the active infection and saved the remaining vision in her right eye, the damage done to the left eye was too severe. A week after the infection was brought under control, the left eye suffered a total retinal detachment, leaving the patient with very limited vision in that eye. This case highlights a critical lesson for medical professionals: when a patient with a weakened immune system does not respond normally to standard antiviral treatment, doctors must look beyond the primary diagnosis. In this instance, the presence of a second, silent bacterial infection was the key to understanding why the initial treatment failed. By identifying and treating both the virus and the bacteria, the medical team was able to stop the disease from destroying the patient's remaining sight, demonstrating that a thorough search for hidden co-infections can be essential in complex medical cases.