WASHINGTON — Chronic fatigue syndrome is a real and serious disease that needs a new name to reflect that – and a straightforward way to diagnose the illness, a government advisory group declared Tuesday.

Patients flooded the prestigious Institute of Medicine with stories of years of misdiagnosis or even being dismissed by skeptical doctors. Tuesday, an IOM panel sought to redefine this long-controversial ailment, setting five main symptoms as simple criteria for doctors to use in making a diagnosis.

And the report called for a new name to replace the “chronic fatigue” moniker that so many patients said belittled their suffering. The choice: systemic exertion intolerance disease, or SEID, to reflect that symptoms worsen after exertion.

People shouldn’t “wander around in the wilderness for years trying to get a diagnosis,” said Dr. Ellen Wright Clayton, a Vanderbilt University specialist on genetics and the law, who chaired the committee.

The report stressed, “It is not appropriate to dismiss these patients by saying, ‘I am chronically fatigued, too.’ ”

Whatever it’s called, the disorder’s hallmark is persistent and profound fatigue – where, depending on the severity, a simple activity like grocery shopping can put someone to bed – often accompanied by memory problems and other symptoms. There’s no medical test for it and there’s no specific treatment.

Tuesday’s report said anywhere from 836,000 to 2.5 million Americans suffer from the disorder, most of them not diagnosed.