Chris Jennings, a top adviser to President Barack Obama who played a key part in the rollout of his signature healthcare law, is leaving the White House for health and family reasons, an aide told Reuters.
Jennings, who previously served in the Clinton administration, was brought on board last year before the flawed rollout of the program created one of the biggest political problems Obama has faced since entering office.
"Chris served the country at a time when he was needed most," White House chief of staff Denis McDonough said in a statement.
"He will be deeply missed but we all wish him the best and know that he will continue to be a key player in health care and always a champion for quality affordable health care for all Americans."
An aide blamed a recent health scare and "other serious family considerations" for Jennings' departure.
Jennings, who had more than 30 years of experience in health policy, was a widely respected expert who advised President Bill Clinton as a senior adviser.
His arrival at the Obama White House was announced in July ahead of what proved to be a critical juncture for the Affordable Care Act, also known as Obamacare.
"It has been a great privilege to work with the President and his incredibly dedicated team on the Affordable Care Act," Jennings said.
"This is the cause of my professional life and I look forward to making continued contributions to that end."