Doctors classify diseases like zoologists classify animals. A new disease, discovered and described, is placed next to diseases with similar symptoms, causes, and prognosis, which helps inform physicians about the best treatments to initially try. Later, when more specific information is known about a disease, that classification may change – just as biologists have dramatically redrawn the Tree of Life thanks to genetic similarities that trumped surface comparisons.
A disease called neuromyelitis optica (NMO), or Devic’s disease, would seem like a pretty easy one to put in its proper place. Since its discovery in the late 19th century, the disease was considered to be a variant of the neurological disorder multiple sclerosis. As in MS, a patient with NMO suffers an autoimmune attack on their nervous system, with the body’s natural defense mechanisms mistakenly killing off the insulation that help neurons conduct signals.
But unlike MS, which occurs throughout the brain and spinal cord, the NMO attack is restricted to the spinal cord and optic nerve, causing the sudden onset of visual problems and muscular difficulties. Untreated cases can lead to blindness and paralysis, said Adil Javed, assistant professor of neurology at the University of Chicago Medical Center.
“The inflammation is very intense in the spinal cord and the eyes, as opposed to multiple sclerosis,” Javed said. “The patients go blind and become paralyzed very quickly as soon as the disease starts. Within a year or two, they can go from walking to a wheelchair or a stretcher.”
Yet the differences were not enough to convince doctors that NMO was anything other than a cousin to MS. Patients with NMO symptoms were sometimes misdiagnosed as suffering from multiple sclerosis, or correctly diagnosed and treated with drugs designed for MS such as interferons. However, during his time as a neurological fellow at the Medical Center, Javed and his colleagues began to notice that NMO might not be as close a relative to MS as the field had thought.
The first clue was in the treatment – “We learned over the years that the interferons, which are the standard treatment for many MS patients, doesn’t work with Devic’s disease,” Javed said. “In fact, in many cases it made them worse.” Another mystery was the symptoms NMO patients shared with another group of diseases, the rheumatological disorders of lupus and Sjogren’s disease. Symptoms of Sjogren’s, including dry eyes and mouth, joint pain, and some organ dysfunction, turned up in a high number of NMO patients, Javed noticed with interest.
“That’s pretty rare that you would have two of these diseases,” Javed said. “So we thought perhaps they are connected.”
That hunch turned out to be true, as Javed and colleagues published in 2008 that an astonishing 80 percent of their NMO patients also qualified for a diagnosis of Sjogren’s disease. And while such patients – predominantly African-American women in their 40’s or older – were unresponsive to the treatments used for MS, they showed improvement with treatments used for Sjogren’s and lupus, including steroid and chemotherapy drugs. Treating NMO as a rheumatologic disease rather than a neurological disease helped patients prevent future relapses that could leave them with permanent damage, Javed said.
“It turns out that most attacks of disease happen in the first five years, as opposed to MS, which is a long, chronic, progressive disease,” Javed said. “We do initial intense chemotherapy for 5 years, then back off to more benign drugs.”
While the intensive treatment can’t roll back the damage done by the first or second attack, it can prevent further decline in vision and motion. That makes it especially important that the proper diagnosis of NMO, rather than MS, is reached early by physicians – an assessment that can currently be made using a blood test for antibodies unique to NMO or MRI imaging.
“The damage in the disease is done if you have an attack. It’s like having heart attacks; if you give an aspirin after a heart attack it’s not going to undo the damage that was done,” Javed said. “But if you were to give a very strong drug from the get-go to prevent that second attack or the third, that’s good. Because if one attack gets you down to a cane, you don’t want to end up in a wheelchair.”