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Go Ask Mom

Go Ask Mom

Acute Viral Myositis: A rare (but terrifying) side effect of the flu in kids

Posted February 25, 2020 9:00 p.m. EST

Sick child

Imagine this – your child is just getting over the flu (or another similar virus) and you can finally see the light at the end of the tunnel. Suddenly, they’re complaining of pain in their legs and can’t even muster the strength to walk or get off the couch.

As a parent, this sounds terrifying. Here’s the good news: If you know what it is, it’s not really that scary. But because it’s rare, most parents have no idea what’s happening and assume the worst. It’s called acute viral myositis.

“Also referred to as benign childhood myositis, this is an uncommon complication that typically occurs at the tail end of a virus – it causes muscle inflammation that can range from mildly uncomfortable to more severe cases where the muscles are so weak, some kids feel like they can’t walk,” says Dr. Edward Pickens, medical director of UNC Pediatrics at Southpoint. “The most common signs and symptoms we see are pretty extreme muscle pain and soreness. Because the calf muscles are more prone to inflammation, some kids with acute viral myositis will walk on their tiptoes, while some kids don’t want to walk at all.”

The good news is that it’s a condition that very rarely requires treatment – other than comfort care such as over-the-counter pain relievers such as Tylenol or ibuprofren.

Dr. Pickens says it typically lasts anywhere from four to 10 days and then it just goes away on its own with no lasting effects. For those not sure when or if to seek treatment, Dr. Pickens says if the pain is really severe or can’t be comforted by over-the-counter medicine, it’s probably worth getting it checked out.

“A simple blood test can confirm myositis, which can be important to rule out other conditions that could mimic the symptoms,” Dr. Pickens explains. While Dr. Pickens acknowledges that it’s hard for parents to do nothing when their child is uncomfortable, he explains that this is one condition that you can typically just watch and wait.

“Complications of myositis are very rare, but we will occasionally see kids going into kidney failure (otherwise known as rhabdomyolysis), which can be life-threatening. Parents should be on the lookout for dark or red urine, which can signal kidney problems. If a kidney problem is suspected, intravenous (IV) fluids will typically flush things out pretty quickly,” he said. But, again, Dr. Pickens reiterates that this complication is extremely uncommon.

Acute viral myositis is most common in kids between the ages of six and eight, and is more common in boys. “There’s a list of viruses a mile long that can cause it, but flu is by far the most common,” Dr. Pickens says.

So there you have it. If your child has been under the weather and suddenly complains of leg pain – chances are, it’s a simple “run-out-the-clock” situation. And just maybe, an extra day of snuggles on the couch.