492
The youngest child ( 2 years old ) was only mildly affected but had Leu - AVP levels similar to her severely affected 8 - year - old brother , suggesting that unknown mechanisms may partially compensate for a deficiency of active AVP in very young children . .
 deficiency of active AVP
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Disease 
Text: {0} 
Answer:
 deficiency of active AVP