Conversation so far:
What year was Irving Thalberg born?
Thalberg was born in Brooklyn, to German Jewish immigrant parents.
Who were his parents?
Jewish immigrant parents, William and Henrietta (Haymann).
Did he have any siblings?
Shortly after birth, he was diagnosed with "blue baby syndrome," caused by a congenital disease that limited the oxygen supply to his heart.
Did this impact him at all in life?
The prognosis from the family's doctor and specialists was that he might live to age twenty, or at most, age thirty.
Where did he go to school?
During his high school years in Brooklyn, he began having attacks of chest pains, dizziness and fatigue.
This affected his ability to study.

Question: What caused his illness in high school?
Self-contained rewrite: What caused Irving Thalberg illness in high school?