Histiocytosis is a disease of the immune system, when white blood cells grow too much in certain areas of body, causing a variety of serious problems. Dr. Kenneth McClain is a professor of pediatrics at Baylor College of Medicine and is one of the few experts on the disease.
"It can be very deadly for little children less than one year of age when it gets in their liver and spleen and we can only cure half of those children. In others, it makes a very bad skin rash that can be extremely irritating and painful. It makes holes in the bones that are painful and can cause collapse of the backbone. It can get into the brain and cause learning problems and problems with balance and motion. It's quite a tricky disease and you have to be always vigilant for a new twist in the way it's working."
Doctors treat only about 300 new cases of histiocytosis every year in the United States, a condition so rare that it's known as an "orphan disease" that gets little attention or funding from the federal government. It's also confusing for parents who may have never heard of the disease or its symptoms.
"It can look like so many other things. An accidental bump on the head, a diaper rash that just won't respond to the normal treatments, cradle cap that is a normal thing in little babies but stays for much too long of time or reappears at a year of age. So you have kind of keep these little things in the back of your mind and say, well that's a little suspicious."
Four-year-old Margaret Smith was diagnosed with histiocytosis when she was about a year old, when her mother Karen noticed a lump behind her ear. Margaret is now recovering after several rounds of chemotherepy.
"There were no symptoms for her. She was happy, active, wasn't quite walking, but that was just because of her age. It was just a lump that appeared behind her ear and that was just where the white blood cells had eaten through that bone and allowed the tissue in there to pop out."
For Beatriz Zadillo, a persistent diaper rash on her two-year-old daguther Stephanie turned into a diagnosis of a disease she didn't know existed.
"It was very shocking because who would figure a diaper rash? There are cases where children just have heat rashes and from there it starts developing. We've gone on it for two year already and it's shocking. You don't know where it comes from."
Because of that, Dr. McClain will begin a 3,300 mile cross-country bike ride on Saturday. The ride is expected to raise $300,000 for histiocytosis research.