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Phenylketonuria ( PKU , OMIM 261600 ) is an autosomal recessive inborn error of phenylalanine metabolism , predominantly caused by mutations in the phenylalanine hydroxylase ( PAH ) gene .
 Chemical: phenylalanine; Chemical: phenylalanine
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: phenylalanine; Chemical: phenylalanine