A pedestrian walks past the Toronto Stock Exchange in Toronto’s Financial District. Photo by Peter J. Thompson/National Post files

Mark Leonard resigned as president of Canada’s Constellation Software Inc. for health reasons, sending the shares to their lowest level in more than a year and prompting an analyst downgrade.

Constellation shares fell 5.5 per cent to $3,910.71 as of 11:40 a.m. in Toronto, erasing $4.8 billion in market capitalization for the Toronto-based company. The stock had briefly plunged 19 per cent.

Chief operating officer Mark Miller was promoted to president. Leonard, who started the company in 1995 and turned it into Canada’s second-most valuable public technology company with serial acquisitions, will stay on the board.

“My first thoughts are with my friend a

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