Most states, including Washington, have child abuse laws that allow some religious exemptions for parents who do not seek medical treatment when their children are sick.Blogger's Note: Due to a quick and careless reading, I had initially understood the news article to be suggesting the family are Christian Scientists, but on second reading, that appears to be incorrect. I still maintain that the law helped to contribute to the teen's death by legitimizing the notion that faith-healing can substitute for actual medical treatment. As the article notes, Washington law makes the exemption for Christian Scientists because their church has the legal muscle which smaller Pentecostal groups do not; this might lead such groups to believe that they should have the same right as the Christian Scientists (although I would maintain the obvious and correct conclusion is that no one should have such a right.)
Washington's law specifies that a person treated through faith healing "by a duly accredited Christian Science practitioner in lieu of medical care is not considered deprived of medically necessary health care or abandoned." Other religions are not mentioned.
Indeed, in 1997, a girl whose family were members of the Colorado branch of the Church of the First Born, died from untreated diabetes. As in the case above, the law in Colorado made an exemption for withholding medical treatment, but the girl's case didn't technically fall under the exemption.
For more on the Christian Scientist led national movement (spearheaded by two Republican members of Congress*) to allow parents to withhold medical treatment from their children on First Amendment grounds, see this article from the Humanist.
*With one of them being a member of The Family.