Dr. B U.K. Li at Wisconsin Children's Hospital in Milwaukee said he has seen the greatest number of children suffering from cyclic vomiting syndrome in the world, more than 1,000 patients.
Because of the large number of patients he sees in the Cyclic Vomiting Syndrome Program he directs there, Li said he has been able to sub-classify various types.
Li credits Kathleen Adams of the Cyclic Vomiting Syndrome Association with bringing the issue forward, seeking doctors – including himself – willing to tackle the disorder.
"In the whole literature, probably there were 30-40 articles over a century," Li said. "It was recognized – so to speak – but there was almost nothing known and nobody cared about it … until several of us got involved in 1993."
Li said working through the disorder's complexities are like peeling the layers of an onion.
"We know stress is involved," Li said. "We know it is very like a migraine – we really think it is a migraine variant – but nobody knows what a migraine is, so that certainly doesn't help."
Doctors also know that the autonomic nervous system that controls the heart rate and blood pressure is involved, Li said, as well as mitochondria – located inside the body's cells and responsible to produce energy.
While studying the family histories of CVS patients, Li said doctors found that 80 percent of the mother's side of the family had migraines, 20 percent of the father's side had them. The concentration on the mother's side is consistent with mitochondrial DNA mutations, Li said.
Mitochondrial geneticist Dr. Richard Boles found two mutations that are highly predictive of having cyclic vomiting syndrome and migraine headaches, Li said.
The disorder can affect anyone at any age. Li said the youngest documented patient was six days old and the oldest documented was 73 when the vomiting disorder started.
Generally, three age groups are affected, Li said. One that starts as toddlers and around kindergarten, such as Julia Benway. Another group that starts in the teen years and may continue into adulthood. The third group at age 30-35.
"The first group tends to get better at the teen age years," Li said. "There is a teen age onset group and we don't know what happens to them, but clearly some of them go into adulthood. And we have adults documented at 30 and 35."