Six pet owners have sued Happiness is Pets, a Chicago-based pet store accused of selling sick dogs purchased from puppy mills or breeding companies known to place profit before animal welfare.
The pet owners "purchased puppies sold by Happiness which falsely represented that its puppies were healthy and came from private and reputable breeders," according to the complaint filed last week.
"In fact, the puppies at Happiness are often sick and come from some of the most despicable and horrendous puppy mills in the Midwest."
At the center of the complaint are six dogs that were plagued with health issues after pet owners bought the animals from the chain of pet stores owned by Ronald Berning, who denies the allegations.
"The lawsuit has absolutely no merit and we're confident that's going to be dismissed," his attorney, David Fish, said.
In July 2009, Stephanie Castillo and her husband purchased a miniature long haired dachshund named Diva. It was months later, after routine blood work and pre-spaying, when owners learned of liver problems, they say.
"We were told if she had not had those blood tests and we went ahead with the surgery to have her spayed, she would have been unable to filter out the anesthesia and she never would have woken up," Castillo told ABC News.
After blood results, the veterinarian suspected a liver shunt or microvascular dysplasia, a genetic condition where blood does not flow properly to the liver, and an ultrasound and, later, a biopsy were ordered.
After a surgical biopsy, it was determined Diva had microvascular dysplasia.
"It wasn't as bad as it could have been but still bad enough to warrant her to be on prescription food the rest of her life," Castillo said. "As well as a pill that she takes to support her liver health.
"Diva has to go every six months to have blood work tested to make sure the condition is not worsening. Due to this genetic disease that she has, she's unable to take any type of medications," Castillo said, including medication for the severe allergies the pup suffers from.
Attorney Fish defended the store's practices. "Happiness has a very strong health warranty, and we stand behind its dog," he said. "Each puppy comes with a health warranty."
The six-store chain has a "Limited Puppy Warranty," which is posted on the company's Website.
The warranty includes a 14-day health warranty, including free veterinary visits and a limited one year warranty against life threatening congenital defects, among other things.
For many of the dog owners, however, the comfort of a familiar veterinarian was who they sought when health problems cropped up, and one was beyond the warranty period.
On Monday, Jan. 2, Lissett Dzieglo and her boyfriend purchased an 8-week-old Miniature Pinscher named Gunner from a Happiness is Pets store in Naperville, Ill.
"By Wednesday or Thursday, he started coughing," Dzieglo told ABC News. "At first, I thought he was getting himself excited and I kept an eye on it. By Saturday, he was having coughing attacks and it would last minutes at a time and would last throughout the day, so I called the vet, and I took him in that Sunday."
Gunner was given shots, and later placed on antibiotics for a cough that was not improving and also for nasal and eye discharge.
The Aurora, Ill., dog-lover, who also owns a 6-year-old Doberman Pinscher, said "it's very upsetting because you have mixed feelings. I'm happy in a way that I purchased Gunner and we're able to care for him."
While "it is a financial hardship, I would never say, 'Oh, I want to get rid of him now,'" she said.
The purchase of a dog that came from an alleged puppy mill is what Castillo finds distressing.
"I just helped the selling of a dog that came into this world on horrible circumstances," she said.