Nothing worries parents more than a sick infant--especially when nobody can figure out what's wrong. For Asher Gould's parents, the uncertainty lasted for the first three years of their son's life. Asher's older brother Sam, now 10, has always been pretty healthy. But a couple of months after he was born, Asher started having trouble feeding and was spotting his diapers with blood. The pediatrician decided he had an allergy to milk. Then, at 9 months, he couldn't crawl or sit up. The diagnosis this time was hypotonia, a vague term that basically means "poor muscle tone." With physical therapy, Asher walked...

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