Article From: "Greg Ryan"   Read full article

Sean Healey, the chief executive of Affiliated Managers Group since 2005, is stepping down as CEO of the asset manager effectively immediately after being diagnosed with amyotrophic lateral sclerosis, also known as Lou Gehrig’s disease.

Another long-time AMG (NYSE: AMG) executive, Nathaniel Dalton, is replacing Healey as CEO, the firm said Tuesday. Dalton had been AMG’s chief operating officer since 2006 and its president since 2011. Healey will remain as the firm’s executive chairman.

AMG…