2072
On the basis of clinical and biochemical observations , the younger boy was considered to have a classical type of the disease , while the older boy had an atypical form characterized by partial impairment of the skin histidase activity and a moderately prolonged half - life of blood histidine .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Disease 
Text: {0} 
Answer:
 None