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Rett syndrome ( RTT ) is a pervasive developmental disorder , primarily affecting girls with a prevalence of 1 in every 10 , 000 births ; it represents the second most common cause of intellectual disability in females .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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