Jaime Snyder had two reasons to be thrilled Saturday.
First, an experimental chemotherapy drug had dramatically shrunk the tumors threatening the vision and brain of her 3-year-old son Jonah.
And second, nearly 600 people had shown up to run through the icy wind in their skivvies to raise more than $100,000 for the Children's Tumor Foundation, which funds research into the neurofibromatosis, or NF, that afflicts her son and thousands of other children.
In Pittsburgh's first Cupid's Undie Run, joggers of all shapes and sizes -- but decidedly favoring the younger demographic -- ran from Buckhead Saloon at Station Square to Downtown and back along the snow-covered sidewalks of the Smithfield Street Bridge.
At 25 degrees and with wind whipping down the Monongahela, it would have been a chilly run in any clothing, but most of the participants did it in some combination of boxers, briefs, panties, bras, chemises and superhero outfits, with an accent on red and pink in honor of Valentine's Day weekend.
Undie Run coordinator Rachel Olbeter, whose 7-year-old son Alex also has NF, said most first-time Undie Run cities are expected to draw 400 people and raise $40,000, so "we've already blown that out of the water."
Many of those who ran Saturday afternoon had connections to NF families. Others just like raising money for charity. And given the physiques on display, some may just have enjoyed getting official permission to run through the streets in absolute minimum coverage.
"If I had a runner's body and I heard there was this race where I could run around in my underwear, I'd probably say, 'Sign me up,' " said Amy Goldstein, a pediatric neurologist and NF expert at Children's Hospital of Pittsburgh of UPMC.
Neurofibromatosis comes in two forms. Even the more common one, NF 1, affects 1 in 3,000 children, so it still qualifies as a rare disease. NF 1 can be inherited from parents or be caused by spontaneous genetic mutations, and it is often marked by benign tumors growing from the nerves that can threaten vision, certain organs or the spine.
About a third of NF cases are mild, Dr. Goldstein said, with children having an abnormal number of freckles or light brown spots on their skin. Another third are marked by small tumors, which in some cases can spread over the entire face and body. That's what affected Vinicio Riva, the facially disfigured man who Pope Francis embraced last year at the Vatican.
The other third of patients can get internal tumors that grow on the optic nerve and threaten sight, or tumors known as plexiform neurofibromas, which can grow inside the torso and threaten breathing or the function of certain organs, she said.
Jonah Snyder, whose family lives in Squirrel Hill, has one tumor growing from the optic nerve behind his right eye, a plexiform tumor growing right in front of that, and another tumor deep in his brain near the hypothalamus, which controls hunger, sleep and other basic bodily functions.
Thanks to the new chemotherapy treatment, known as AZD6244, the brain tumor has almost disappeared, and another one has shrunk 30 percent, Ms. Snyder said. "This is his second type of chemo and it's almost like a miracle drug."
While the NF tumors aren't cancerous, chemotherapy still works when they are fast growing, because most chemo is aimed at halting the proliferation of quickly dividing cells.
One of Saturday's participants was Jessica Yurko, 25, of Irwin, who knows April Hanahan of Monroeville, whose 4-year-old daughter Kelsey Marie was diagnosed with a brain tumor and possible NF last year. Kelsey's Team raised about $3,400 in pledges, including $500 raised by Ms. Yurko. When she was asked how she would do running across a bridge and back, she laughed.
"We're crossing a bridge? I'm never going to make that!"
Tim Bryner, 29, of Bellevue, did make it, and was glad to be standing back in the warmth of Buckhead Saloon afterward, dressed only in briefs and his running shoes.
"I've never done anything like this," said Mr. Bryner, part of a team from LA Fitness in Monroeville. "When I signed up, I didn't think it would be bad, until they said we were crossing the Smithfield Street Bridge, because I used to walk across that bridge when I was going to school and it was cold when you were fully clothed."
Ryann Heverly of Greensburg, who was running with her husband and a friend, said the saving grace was that "you're numb halfway through so you don't notice it as much." Still, she slipped on the snow-covered sidewalk, her husband, Mark, said, paying an extra price for her generosity.
"It was a small sacrifice for the kids on Valentine's Day," she said with a laugh.
As for Jaime Snyder, she raised about $10,000 for the event -- but she wasn't planning to run.
Her body showed why: she's due to give birth in nine days to a daughter, and prenatal testing has already shown the girl won't have NF.
She isn't sure what the future holds for Jonah.
"This disorder is so ridiculous, in that you can have such success in treating it, and the next day your child could get diagnosed with a tumor somewhere else. But my hope is that this drug Jonah has been taking gets rid of all his tumors and he spends the rest of his life tumor-free."
Mark Roth: email@example.com.