I thought my daughter was obese because she wouldn't stop eating... I was shocked to learn the real reason

A mother-of-two has revealed how her daughter's mysterious weight gain was a sign of a rare genetic disorder.

As Ciara Keown's four-year-old daughter, Harper, entered pre-K, she began suffering meltdowns over fitting into her clothes and shoes.

Despite being 'very lean' as a toddler, Harper had packed on 30 pounds within just a few months due to an insatiable appetite.

Keown and her husband had struggled with their own weight since they were kids, and the parents assumed Harper was following in their footsteps.

'We just thought it was our bad habits rubbing off on her,' Keown told the Daily Mail.

The family visited an obesity clinic near their home in Chattanooga, Tennessee, which counseled them on dietary swaps and other lifestyle changes, but Harper's weight continued to climb.

By the time she was seven, she weighed over 100 pounds, twice as much as a typical second grader.

Children would push her down on the playground and call her 'fat,' forcing the family to pull her out of school. 'She shut down during that time,' Keown said. 'No kid should have to go through that.'

Unable to explain the weight gain despite diet and exercise, the clinic suggested Harper undergo genetic testing last year, which revealed she had Bardet-Biedl syndrome (BBS), a rare condition affecting just under 5,000 Americans that causes weight gain and constant, insatiable hunger.

The condition usually manifests early in childhood and progresses over time and affects nearly every major organ, eventually leading to vision loss, kidney failure and developmental delays.

Further testing showed Harper's younger sister, Luna, also had BBS, though she hadn't yet displayed symptoms, and both of their parents were carriers for the mutated genes that cause the condition.

Keown said: '[The doctor] was just mind-blown. She was like, "I've never heard of this before."'

BBS is caused by mutations in one of at least 24 different genes, most commonly BBS1 and BBS10, which provide instructions for the formation of cilia, hairlike structures on cells that help them relay sensory information like light, sound, smell and taste.

These mutations cause a dysfunction of the brain's melanocortin-4 receptor (MC4R) pathway, which controls hunger and satiety. If the receptor is mutated, it cannot communicate to the brain that the body is full, leading to uncontrolled eating.

Like Harper, most patients start gaining excess weight around three to five years old, which continues into adulthood, often despite dietary changes and exercise.

Luna also started to gain weight around age four, jumping from 30 to 80 pounds within a few months, more than double the weight of the average preschooler.

After their diagnosis, the girls were put on topiramate (known as Topamax), an anticonvulsant used off-label for weight loss, and Vyvanse, a stimulant used to treat ADHD and binge eating disorder, to help slow their ravenous hunger.

They also take setmelanotide, a daily injection under the brand name Imcivree that targets the dysfunctional MC4R pathway.

'It's a complete gamechanger,' Keown told the Daily Mail.

With the help of the medications, as well as dietary swaps and exercise, Harper has lost 30 pounds so far and Luna has lost 10 in the last year.

Since losing the weight, Harper has regained the confidence to return to school, where she most enjoys spending time with her friends.

Keown said: 'She's braver now, like she'll stand up for herself now, whereas in kindergarten, she wouldn't stand up for herself.

'She's not had any problems. She absolutely loves [school].'

While the girls have lost weight, BBS still affects multiple major organ systems, leaving them with a team of about 10 specialists between the two of them. Luna is in the early stages of chronic kidney disease, while BBS has attacked Harper's liver.

In children, kidney disease can lead to growth issues, cognitive problems, anemia and incontinence. If it progresses, a kidney transplant may be necessary. And children who suffer from liver diseases may experience fatigue, nausea, a swollen abdomen, jaundice and itching.

About half of children in liver failure will eventually need a transplant.

'We live in and out of doctor's [offices],' Keown said.

The girls both have accommodations at school for their condition, including extra time during tests due to dyslexia, which BBS raises the risk of, additional restroom breaks due to kidney issues and rest time from gym class.

The Keown family is now working to spread awareness of BBS and connect with other families across the US. Harper has even helped other children with the condition work up the courage for their daily Imcivree shots.

Keown said: 'It's just one step at a time. I was scared at first, but it's not a death sentence, so when [other] moms reach out, I try to express that to them.

'I've heard stories of remission, so I really just want the girls to go into that. I want them to be able to to be able to manage all of this on on their own. I want them to be able just to handle this, be healthy, not have to have to have many doctors, just regular checkups every now and then in the future.'