At just 13 years old, Charlie Knuth, of Darboy, Wisc., has known more pain than most others do in a lifetime. The teen, who suffers from epidermolysis bullosa, a rare disease that causes his skin to blister incredibly easily, is near-constantly wrapped in bandages to protect his fragile skin. He takes special baths to soothe his sores, which can form from the slightest touch and are lanced before he is covered in fresh dressings. But the so-called “butterfly child” — a name often given to EB sufferers as their skin’s fragility is similar to that of a butterfly wing — has another battle ahead: cancer.

“It’s unimaginable,” Trisha Knuth, Charlie’s mother, told Fox News. “Even as his mom, when I see him taking it in stride, I can’t even believe that he can.”

BOY, 2, HAS RARE 'SCALE'-LIKE SKIN CONDITION THAT AFFECTS 1 IN 500,000: 'HE’S OVERCOME SO MUCH'

Charlie’s biological parents abandoned him at the hospital shortly after his birth. Knuth and her husband, Kevin, had long fostered children with complex medical needs. But just weeks before they received a call about Charlie, they were readying to let their license expire; the tragic cases were simply becoming too much. Even so, Knuth said she couldn’t say no to Charlie — she knew to do so was likely a death sentence. They began the lengthy adoption process shortly after bringing him home.

“When I went to the children's hospital in Milwaukee, he was slathered from head-to-toe in Vaseline," she recalled. "Nobody ever came for him. I worked with the nurses and learned his care — but EB is so rare that many hospitals don't know how to care for those with [the condition]. They sent me home with morphine and a few things and it was a learning process from there.”

Thirteen years later, Charlie “didn’t end up dying, he ended up thriving,” she said. When he was 5 years old, he underwent an experimental skin grafting procedure at the University of Minnesota in an attempt to make his skin stronger and less prone to blistering. Knuth called it a “transformation” for her young son, who had two “really good” years before his body rejected the graft and he began to suffer from aplastic anemia, a potentially deadly condition that occurs when the body doesn't produce enough red blood cells.

In 2012, he underwent a stem cell transplant in an attempt to treat his severe EB. He was hospitalized for six months but eventually pulled through.

“He’s done pretty well after that second time. But he is constantly wounded, very fragile,” said Knuth.

But in recent months, Charlie began to complain of a sore throat — not uncommon for those with EB, as blisters can form on the inside of the body as well on the outside. The mouth and throat are commonly affected. But there were no visible blisters, raising his doctor's suspicions. A CT scan later revealed enlarged lymph nodes in his neck and armpits. A biopsy later confirmed lymphoma, a type of cancer that affects the body’s lymphatic system. Knuth called the diagnosis “another hurdle in his very hard life.”

“The pain was masked by EB. It’s hard to tell what’s what because EB causes so much pain,” she said.

Cancer treatment — often consisting of chemotherapy, radiation, and surgery — is hard enough on an average person’s body. But those with EB face an entirely different battle; Knuth said nurses inserting an IV can’t use medical tape to help attach the drip, as the adhesive rips her son’s skin when removed. Oxygen and anesthesia masks are often a struggle as well, as are blood pressure cuffs.

“How do you treat someone who can’t be touched?” Knuth questioned, noting she has gone into the operating room with Charlie in times past to ensure he is not injured. “You can’t even imagine. [It’s like] being burned every day, and then bandaged, and now undergoing cancer treatment — it boggles the mind.”

When speaking to Fox News, Knuth and Charlie were in Minnesota, where doctors are working to build a treatment plan. The day after Christmas — which the pair are celebrating in an Airbnb — Charlie is slated to undergo a procedure to remove fluid from his spine and bone marrow from his hips. One of his affected lymph nodes will be taken for further testing.

In the meantime, Kevin is home with the couple’s 8-year-old adopted daughter, who also suffers from EB.

"He puts on a great outward attitude, but I know there is trauma." — Trisha Knuth

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“He is very brave and resilient and funny,” said Knuth of Charlie. But in addition to the physical pain, “He does have emotional pain; he puts on a great outward attitude, but I know there is trauma.”

When asked how she and Kevin manage it all, Knuth acknowledged theirs is a “crazy life.” But, she quickly noted, “I am very happy with this life. It’s hard. But when I die, I'll know my life was fulfilled and great.”