Devic’s disease, now more commonly called neuromyelitis optica spectrum disorder (NMOSD), can be fatal, but most people survive it. Mortality rates in recent studies range from about 4% to 13%, a significant improvement over older estimates that placed the five-year mortality rate as high as 32%. The outlook depends heavily on how quickly the disease is diagnosed, how often relapses occur, and whether effective treatment is started early.
How Often Devic’s Disease Causes Death
Before modern blood tests could identify the disease accurately, studies reported that roughly one in three patients died within five years, with a median survival of about 17.5 years from diagnosis. Those numbers painted a grim picture, but they reflected an era when many patients were misdiagnosed with multiple sclerosis and given treatments that could actually worsen NMOSD.
Contemporary studies tell a different story. A large registry study from Argentina found an 11-year mortality rate of 7%. A Chinese study of 569 patients reported overall mortality of 4.2% during follow-up. A multi-ethnic cohort of 427 patients found a 7% mortality rate with an annual death rate of 0.68 per 100 patient-years. These numbers are still sobering for a neurological disease, but they represent a real improvement. For comparison, NMOSD patients are roughly 12 times more likely to die from their disease than patients with relapsing-remitting multiple sclerosis.
What Causes Death in NMOSD
The most common cause of death is respiratory infection, accounting for nearly half of all deaths in one large study. NMOSD can leave patients severely disabled after attacks, and immobility raises the risk of pneumonia and other infections. Secondary infections of all types were responsible for about 63% of deaths in that same study.
The second major cause is respiratory failure from spinal cord damage. When NMOSD attacks the upper spinal cord in the neck region, the inflammation can extend across long segments and disrupt the nerves controlling breathing. This type of attack accounted for about 17% of deaths. Suicide was also identified as a cause of death in roughly 8% of cases, reflecting the heavy psychological burden of living with a disabling, unpredictable disease.
The Disability Trajectory
Even when NMOSD doesn’t kill, it often disables. In a study of 46 patients with the relapsing form, 42% needed a walking aid within five years, and that number climbed to 53% by ten years. By 15 years, nearly one in four patients had reached the most severe disability level. The average relapse rate was about 1.3 attacks per year, and each relapse carries the risk of permanent damage to the optic nerves or spinal cord.
Two factors most strongly predicted how quickly disability accumulated: the severity of the first attack and how frequently relapses occurred afterward. Patients who had a short gap between their first and second attack, or who relapsed often, tended to accumulate disability faster. Age at onset also mattered, with older patients generally faring worse.
What Makes Some Cases More Dangerous
NMOSD is driven by an antibody that attacks a water channel protein found on cells in the spinal cord and optic nerves. Patients who test positive for this antibody (called AQP4-IgG) have a more clearly defined disease course, but also tend to have more severe relapses. Having a coexisting autoimmune connective tissue disease, such as lupus or Sjögren’s syndrome, significantly raises the risk of frequent, aggressive relapses. In one study, that coexisting condition increased the odds of highly active disease roughly sixfold.
Certain blood markers also signal a more aggressive course. Elevated levels of homocysteine, an amino acid linked to inflammation, were associated with greater disability during acute attacks. Higher rates of antibody production in the spinal fluid pointed to more active disease as well.
How Modern Treatments Have Changed the Outlook
The biggest shift in survival came from two developments: a reliable blood test that distinguishes NMOSD from multiple sclerosis, and targeted medications approved specifically for the disease. Before these existed, many NMOSD patients were treated with MS drugs that can actually make NMOSD worse, accelerating disability and raising the risk of fatal attacks.
Since 2019, several targeted therapies have become available that work by blocking specific parts of the immune system responsible for NMOSD attacks. These medications have dramatically reduced relapse rates and slowed disability progression, particularly in patients who test positive for the AQP4 antibody. However, they are not without risk. Because they suppress parts of the immune system, serious infections can occur. One real-world study of a targeted therapy reported serious infections in 13% of patients.
Early and accurate diagnosis remains the single most important factor in survival. The current international diagnostic criteria, established in 2015, allow doctors to diagnose NMOSD after a single attack if the AQP4 antibody is present. This means treatment can begin before a second attack causes irreversible damage, a shift that has likely contributed to the declining mortality rates seen in recent studies.
What Survival Looks Like Today
For patients diagnosed promptly and started on appropriate preventive therapy, the prognosis is considerably better than the statistics from even 15 years ago suggest. The mean disease duration at time of death in one large cohort was 6.9 years, but this figure is skewed by patients who were diagnosed late or treated with the wrong medications. Patients who remain relapse-free on modern therapies can live for decades with the disease.
The critical variable is relapse prevention. Each attack carries the potential for permanent neurological damage, and the cumulative effect of multiple attacks is what drives both disability and mortality. A patient who experiences one or two attacks and then remains stable on treatment faces a fundamentally different future than someone who relapses several times a year. This is why neurologists treat NMOSD aggressively from the start, with the goal of eliminating relapses entirely rather than simply reducing their frequency.