Despite drinking constantly, their bowel movements were hard as golf balls and "actually hurt coming out," he said.
"We knew something wasn't right," said Partington.
The first clues came when Jenna went into the hospital for a severe flu. She was kept for two weeks, spending half the time in the pediatric intensive care unit. Her body had begun to cramp up with dehydration.
"I was changing her diaper and every time I pulled her legs down, she started crying," he said. "The doctor said she was a medical marvel -- he couldn't figure it out."
The diagnosis of cystinosis was finally made in March 2006 by geneticists at Scripps Institute in San Diego, where much of the research on the disease is taking place.
Patrick's diagnosis followed after doctors tested for white blood cell cystine counts.
Both Partington and his wife Teresa carry a recessive gene for the disease. The twins are fraternal, so each independently has a 1 in 4 chance of inheriting both genes.
Odds were so rare of both children getting both genes, "We should've purchased a lotto ticket that day," said their mother Teresa Partington, 39, who has since dedicated her life to research and education through Jenna & Patrick's Foundation of Hope
Recently, she talked to the twins' classmates when Jenna said children had said her breath was bad. The medicine causes a rotten egg sulfphur smell which emits from every pore.
"I felt that enlightening the class would make a difference because I believe children, given the opportunity, can grow to understand some of life's most complicated situations," said their mother.
Somehow, their children adapt to their treatment regimen. "The kids haven't known anything different," said Kevin Partington. "It's not perfect, but it's not as overwhelming as it was in the beginning. It's a routine as a family."
In addition to seven pills twice a day, they down a pomegranate-like cocktail of polycitric acid, iron, calcium, iron and vitamin K, among other ingredients. "It's terrible tasting," according to Partington. "But they shoot that down and go off to school."
All day, they drink water and take bathroom trips every 35 minutes. Before bed, they repeat the routine and though they don't have to be woken for another pill now, they are up to use toilet.
"Usually, they pee a lot in their sleep and we have to change them," he said. "If we woke them up every time, they wouldn't sleep. Their beds are wet every morning."
Patrick was found to have high cholesterol and so both children are now on statins, which their parents fear can cause memory loss.
As it is, they struggle with spatial and visual deficits, which are part of the disease. Since starting school, they are showing some dyslexia.
"Physically, they are not as vital as other kids," said their father.
"Hydration is a big problem and in Sacramento when it gets to 100 degrees...they don't sweat," he said. "Sports like soccer are not an option -- they'd wilt like flowers. But they are able to keep up."
The biggest challenge is psychological.
"It's really hard for us -- they are our only two kids," said Partington. "We can't compare to other kids we've raised.
"We don't know when they're not doing their homework if they don't get it like any other kid, or because of the cystinosis. Or are they just being precocious 7-year-olds playing their mom and dad. There are so few cases out there to share those ideas with."
But his wife says, raising their twins, despite the odds, is "ultimately rewarding."
"We strive to teach our kids and those around us that a person can rise above just about anything by treasuring what's important and doing good," she said. "I would choose happy kids over healthy, though I never imagined I would have to make such a choice."