or chiefly Brit  hy*per*phe*nyl*al*a*nin*ae*mia  n :  the presence of excess phenylalanine in the blood (as in phenylketonuria) hy*per*phe*nyl*al*a*nin*emic or chiefly Brit  hy*per*phe*nyl*al*a*nin*ae*mic  adj 
 
 
 
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