<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by adenosine deaminase deficiency ? [/INST] Adenosine deaminase deficiency is very rare and is estimated to occur in approximately 1 in 200,000 to 1,000,000 newborns worldwide. This disorder is responsible for approximately 15 percent of SCID cases. </s>