Rare condition called acute flaccid myelitis has been reported across the country.

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CDC is trying to figure out what is causing polio-like disease in children. Getty Images

A mysterious polio-like illness has affected more than 150 children this year, according to reports from the U.S. Centers for Disease Control and Prevention (CDC).

The condition – known as acute flaccid myelitis (AFM) – causes rapid muscle weakness in one or more limbs along with damage to the spinal cord’s gray matter.

The sudden spike in reported cases concerned health experts, as they still don’t know what causes AFM or how to best treat it.

Now, new research has found that the symptoms of AFM overlap with other diseases, making it very difficult to diagnosis.

Researchers from Johns Hopkins University recently analyzed patient data from several AFM cases and found that a significant chunk of children had been misdiagnosed.

The research team hopes to help patients receive more accurate diagnoses with clearer, more defined diagnostic criteria that’s detailed in their study, which published in JAMA Pediatrics late November.

In order to distinguish AFM from other similar diseases, the researchers reviewed the medical records and available MRIs of 45 cases that were thought to be AFM.

The team found that only 75 percent of the diagnosed cases were actually AFM. The researchers then compared the characteristics of the definite cases with other viable alternatives.

The patients who did in fact have AFM had a fever or viral infection prior to experiencing weakness in their limbs. On top of that, they lost function of their limbs in one side of their body first — or asymmetrically — with weakness often starting in one limb before advancing to all four.

Those with AFM had a significant amount of white blood cells in their spinal cords and less protein in their cerebral fluid than patients with similar diseases, the study stated.

AFM only caused damage in the gray matter in the spinal cord – which contains nerve cells responsible for muscle contraction – whereas other diseases also showed damage in the white matter and the brain.

According to the CDC, less than 1 in 1 million children contract it each year. Because AFM is so rare, most physicians haven’t seen it before.

“We do not yet have a definitive blood test or MRI that is specific to AFM, so our diagnosis relies on the overall clinical picture — including blood tests and imaging,” Dr. Devorah Segal, a pediatric neurologist at Weill Cornell Medicine and NewYork-Presbyterian, told Healthline.

“There is a lot of overlap between AFM and other disorders that may have similar symptoms and test findings,” Segal added.

AFM evolves over time and varies from case to case. The condition often begins with a fever, respiratory, or gastrointestinal symptoms before advancing to muscle weakness and paralysis.

So, oftentimes, AFM can look quite similarly to other neurological disorders — especially in the beginning stages — before it develops into a pattern more specific to AFM, says Segal.

AFM is commonly misdiagnosed as other illnesses that affect the nervous system and spinal cord such as traverse myelitis and spinal cord stroke. Demyelinating syndromes, Guillain-Barre syndrome, Chiari I myelopathy, and meningitis are frequently mistaken for AFM — and vice versa — as well.

“Misdiagnosing AFM can lead to improper and delayed management, which can lead to a worse prognosis, especially if the wrong treatment is given,” Dr. Daniel Ganjian, a pediatric obesity specialist at Providence Saint John’s Health Center in Santa Monica, said.

For example, according to Ganjian, AFM is often confused with transverse myelitis. And while immune suppressants are effective in treating transverse myelitis, these medications can significantly worsen AFM.

The last thing physicians want to do is give patients a medication that can further suppress the body’s ability to fight an infection.

Currently, the cause of AFM is unclear. However, the CDC believes it may be linked to poliovirus, nonpolio enterovirus, adenoviruses, and West Nile virus.

“Most patients with AFM had a preceding respiratory illness, raising the question whether there is a viral cause of AFM,” Dr. James Wood, an infectious disease physician with Riley Children’s Health at Indiana University, said. “Additionally, there is some evidence supporting an association between an outbreak of a virus, enterovirus D68, and the recent increase in cases of AFM in the United States.”

In addition, environmental toxins and genetic disorders have not been ruled out, the CDC reported.

Although the cause remains unknown, there is a lot of research currently underway to examine the etiology of AFM, says Wood.

At this point, there is no official treatment for AFM either.

“Most people with AFM have been treated with either a medicine, which alters the immune system, and/or an antiviral agent. However, there is no evidence to show these therapies helped or harmed patients with AFM,” Wood explained.

Healthcare providers have noticed that, in general, children respond better to immunoglobulin — antibodies that can mark dangerous pathogens as invaders so the immune system can eliminate them.

Corticosteroids, plasma exchange, nerve surgery, and antiviral therapy have been considered as well — though all are still unproven. Physical and occupational therapy are believed to help AFM patients control and move their limbs.

While we still have a lot to learn about AFM, this study is a crucial step in helping healthcare providers determine what may cause and cure the disease.

Researchers have found that some patients are being misdiagnosed with acute flaccid myelitis (AFM) are being misdiagnosed. They found that only 75 percent of the diagnosed cases were actually AFM.

AFM is commonly misdiagnosed as other illnesses that affect the nervous system and spinal cord — such as traverse myelitis and spinal cord stroke.

Doctors don’t know what cause the disease, and until we know more they recommend ensuring children are up to date on their vaccines and protecting them against mosquito bites by using mosquito repellent.

Lastly, disinfect your child’s toys and always, always wash your hands.