Ben Liestman peeked into the backroom of the Osseo Vacuum shop. He said he could see a Dyson DC24.

"I don't see one," said the shop's owner, Jason Erickson.

"I do," said Ben.

"Oh, you know, there is one," said Erickson, pulling out a forgotten, dusty upright vacuum cleaner in need of repair.

Ben's face lit up.

For the next 20 minutes, he subjected the old vacuum to an extensive inspection: Turn the switch on. Turn it off. Extend the handle. Retract the handle. Unlock it from the upright position. Return it to the upright position. Repeat. He ran his hands over the accessories and lay on the floor to study the brushes.

There were tears when it was finally time to go, even though there were several vacuum cleaners waiting at home, including four toy vacuums.

Ben, who just turned 6, is obsessed with vacuum cleaners.

It's part of a quirky, often endearing mix of personality traits that Ben has — along with health and developmental challenges — because of a rare, little-known genetic condition called Williams syndrome.

It was once called the "cocktail party syndrome" because Williams syndrome kids like Ben are so talkative, friendly and empathetic.

At a restaurant, "Ben will want to get up and go and say hi to everyone at every table because he just wants to make sure everyone is doing good," said his father, Joel Liestman.

A bit like puppy dogs, Williams syndrome kids think everyone is a friend, and everyone is interesting. But some things are particularly fascinating. For Ben, that's vacuum cleaners.

"Some of his first words were 'crevice tool,' 'upholstery tool,' " Joel said. "He could probably identify the logo of vacuums before he could identify his shapes: 'That's a Dirt Devil. That's a Shark. That's a Hoover.' "

Ben likes to watch and imitate YouTube videos of vacuum demonstrations. A request to visit a grandparent will be expressed, "Can we go to Grandpa Bob's? I want to see his Shark Rocket Deluxe."

In addition to toy versions of Dyson and Dirt Devil models, Ben owns a flexible crevice tool he often sleeps with.

When Ben learned that stores including Home Depot, Menards and Target have whole sections of vacuums, "his jaw just dropped," said Liestman, an actor, singer and theater teacher. "He needed to look at all of them."

Best of all is when Ben's parents take him to Osseo Vacuum, a sales and repair shop not far from where the family lives in Maple Grove. "Osseo Vacuum is Valhalla," Joel said. "He could — and has — spent hours there. The guys who run it think it's great and are always willing to talk with him."

When another customer comes in, Ben might ask them what kind of vacuum they have. Sometimes people ask Ben for advice on which vacuum they should get.

When it's time to leave the store, Ben will hug and kiss the floor models that are about as tall as him and say, "Thank you, vacuum."

Once one of his favorite vacuums at the store, a limited-edition Dyson DC25 Blueprint, was sold. Ben went through the well-known stages of grief, asking, "Did someone steal it?" And "The vacuum's coming back, though?" And "But it's my favorite."

"I think he took it harder than when the dog went to doggy heaven," said Joel, who made a poignant short YouTube video about the loss.

You can guess what Ben wanted for his sixth birthday this month: another vacuum.

"This is a hilarious aspect of our life with Ben," Joel said.

"It's sort of all vacuums, all the time," added Ben's mother, Jennifer Liestman.

Abilities and challenges

Williams syndrome affects only one in 10,000 people worldwide. An estimated 20,000 to 30,000 people in the United States have the condition, which was first recognized in 1961. (In comparison, one in about 700 babies are born with Down syndrome in the United States, and about one in 70 children have been identified as having autism spectrum disorder.)

Some adults who have Williams syndrome don't know it because it is so rarely seen.

"There's very little awareness among most doctors," said Tim Boatman, a Minneapolis man whose 26-year-old son has Williams.

Genetic testing techniques can accurately determine whether someone has the condition. But families of Williams children say they can often identify another person with the condition based on some distinctive characteristics: elfin-like facial features with a small upturned nose, small chins and a lacy, white starburst pattern in the eyes. A strong affinity and emotional response to music. And an engagingly social personality.

"They know how to light up a room. They're great at parties," said Terry Monkaba, executive director of the Williams Syndrome Association.

"We're very outgoing. We're super-funny," said Ben Boatman, Tim's son.

But Williams syndrome is also often accompanied by life-threatening cardiovascular problems and other health issues. Intellectual or learning disabilities can include difficulty with spatial tasks, manual dexterity, abstract reasoning and math. As adults, people with Williams often need help handling money, driving and living independently.

Despite being highly social and empathetic, people with Williams can be isolated and have difficulty making deeper emotional connections, in part because they have a hard time mastering the complicated social nuances needed to fit in as adolescents or adults.

"It's kind of like they have 1,000 friends, but no best friend," said Andover resident Andrea Haglund, whose 12-year-old daughter, Elaina, has Williams syndrome.

Their inclination to trust everyone also means sometimes they can be exploited.

"Teaching stranger danger is really hard," said Joel Liestman. "Literally everyone is immediately a friend."

And there's often an unusual fixation with everyday items or occurrences. People with Williams might be fascinated by flags, athletic jerseys, rainstorms, running water, fire trucks. Ben isn't the only Williams child to be obsessed with vacuum cleaners.

Williams syndrome children often have sensitive hearing. Besides vacuums, Ben has been fascinated with noisy things such as smoke alarms, wood chippers and hand dryers in public bathrooms.

"He has sensitivity to loud noises, but he's also attracted to them," Joel said.

Because of genetic tests given to Ben after he was born prematurely, he was diagnosed with Williams syndrome as an infant. He attends a regular kindergarten class at Rice Lake Elementary School in Maple Grove with assistance for speech, occupational and physical therapy.

Although he's had surgeries for his eyes and for a hernia, he's avoided the heart problems that many Williams children experience.

"We've been lucky," said his mom, Jennifer, resident casting director at the Guthrie Theater in Minneapolis.

Joel and Jennifer realize it will take hard work to keep their son as close to his peers as possible. The ultimate goal is for Ben to live as independently as possible as an adult.

"I think he's starting to notice there's a difference between his peers and him," Joel said. Joel's response is to tell his son that everyone's journey is different.

Some parents of children with Williams say the world would be a better place if everyone had a bit of the syndrome, if everyone were as empathetic as their children.

"They have such a capacity for compassion and kindness," Jennifer said. "As a whole, they're just so openhearted."

"He's just so happy with life," Joel said of his son. "The things that bring him joy bring him great joy."