The San Diego Union-Tribune, Dec. 28, 2016

Polio-like syndrome has no known cause

Nearly 60 cases of a rare polio-like syndrome have been identified in California since 2012, a study in the Journal of the American Medical Association reported Tuesday. And despite intensive investigation, the cause remains unknown.

Called acute flaccid myelitis, the syndrome is characterized by a quick onset of muscle weakness in one or more limbs, along with evidence of spinal cord motor neuron damage. Children are most affected. Out of the 59 cases, the median age was 9, with 50 cases in people younger than 21.

The illnesses occurred between June 2012 and July 2015. In most cases, the weakness lasted for at least several months. For the 45 patients with follow-up data, 38 had persistent weakness at the followup. The followup occurred at a median time of 9 months, spread over a range of 3 to 12 months. Two patients, both immune-compromised, died within 60 days of diagnosis.

"Although the syndrome described is largely indistinguishable from poliomyelitis on clinical grounds, epidemiological and laboratory studies have effectively excluded poliovirus as an etiology," the study stated. Its first author was Dr. Keith Van Haren, a neurologist at Stanford University Medical Center.
Researchers examined records collected at the request of the California Department of Public Health, which acted after learning of three such cases in the fall of 2012. This was unusual, the study stated, because no such cases had been identified in the previous 14 years.

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