A spokesman for Flaherty announced in January 2013 that he was being treated for bullous pemphigoid, an autoimmune disease that creates fluid-filled blisters near areas of skin that often flex, such as the upper thighs and the abdomen.
Most patients can have the condition under control within months, and symptoms can disappear completely within one and a half years. It is generally treated with anti-inflammatory, corticosteroid or immunosuppressant drugs, and the latter can create difficulties for people who suffer from other illnesses.
Those who have bullous pemphigoid are at an increased risk of strokes, which happen to blood vessels in the brain, according to the American Heart Association.
It is not clear whether there is any connection between Flaherty's heart attack and the disease.
Flaherty came forward about the disease when he appeared to have gained weight and had a fuller face. His appearance was attributed to his medication.
He often appeared tired in the months following the revelation, sending his press secretary to events he would normally attend himself. Concerns about Flaherty's health flared up again in December 2013, when he appeared weak and had difficulty climbing out of a car at a meeting of finance ministers in Meech Lake, Postmedia News reported.
He spent much of an hours-long meeting in silence, sometimes closing his eyes and leaving Minister of State Kevin Sorenson to chair the proceedings.
Flaherty, 64, announced his resignation from cabinet on March 18, though he said it was unrelated to his health.
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