A concerned mother in Washington, D.C. realized her daughter's missing teeth were symptoms of an underlying neurological condition.
Deanna Rennon, 39, said her youngest daughter, Erica, who was born in 2006, appeared at first to be no different from her older siblings. A while after her birth, however, Rennon soon began to realize something wasn't quite right with her child, the Washington Post reported.
Erica was unusually small, prone to respiratory infections, and slow to develop. She reportedly could not roll over until she was 7 months old or sit up on her own until 8 months.
She was also missing her front teeth, which never grew in, and had to drag herself by her arms when crawling on all fours.
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Rennon, a married mother of four, said she first took her daughter to a physical therapist at the recommendation of a pediatrician. After five months of therapy, however, she was told her child was making no progress and should see a neurologist.
An MRI scan performed at Children's National Medical Center in D.C. in November 2008 revealed that Erica suffered from leukodystrophy, a group of genetic disorders that affect the brain. Children with leukodystrophy are deficient in white matter, which slows down nerve signals in the brain and impairs neurological functioning.
Although doctors identified the generic group of diseases that Rennon's daughter suffered from, which includes at least 50 different known forms, they were not able to pinpoint the exact kind of leukodystrophy afflicting the child.
In September 2009, however, Rennon came across an article in an online medical journal that described children with similar symptoms as her daughter, including missing and misaligned teeth, speech and motor problems.
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Renner immediately brought the article to the attention of Adeline Vanderver, the pediatric neurologist assigned to her daughter's case.
Her fortuitous discovery eventually led to Erica being diagnosed with 4H, a rare type of leukodystrophy disorder, as well as the discovery of the specific gene, POLR3B, that causes the condition.
Vanderver, a researcher at the National Institutes of Health in D.C., said the child's missing front teeth were a "crucial clue."
"It was a lot of serendipitous events," she said, adding that, "... so many little puzzle pieces come together. For years, these children walked around with no front teeth, but nobody noticed that, because they were seen by neurologists," who focused on their brains.
The identification of the gene responsible for the disorder has led to diagnoses in hundreds of cases that were previously unknown, Vanderver said.
Erica, who is now 9 years old, cannot stand without support and will likely have to use a wheelchair in her adolescence. The child's life expectancy is unclear, since many people with 4H die in their teens and 20s.
"My biggest concern for her is that she has friends and fun and is part of the family and giving her everything we possibly can," Rennon said.
According to Right Diagnosis, leukodystrophy is classified as a rare disorder by the National Institutes of Health's Office of Rare Diseases, which means it affects less than 1 in 200,000 people in the U.S. population.