Overstock CEO Patrick Byrne to Take Medical Leave

Overstock.com on Monday said its founder and Chief Executive Patrick Byrne will take an indefinite personal leave of absence for medical reasons.

Mr. Byrne, who in a letter to shareholders said he has been battling stage 4 hepatitis C, recommended the company's general counsel and veteran Internet and tech executive Mitch Edwards take the helm in the interim.

In the letter, Mr. Byrne said he has finished treatment. It is unknown if Mr. Byrne will return to work, the company said.

"I think I have it beat but only time will tell," he said, noting that he contracted the infection in 1984 in China "when a barefoot doctor sewed up a head wound under less-than-ideal conditions."

Hepatitis C is a liver infection caused by a bloodborne virus, according to the Centers for Disease Control and Prevention. For most people, it is a chronic illness and can lead to long-term health problems.

Mr. Byrne said the firm is doing well and forecast pretax earnings of $40 million in 2016. He called Mr. Edwards "an outstanding full-spectrum entrepreneur" who "has learned our business, and understands our efforts to revolutionize the capital markets."

Mr. Edwards, who has been with the company since August, was previously finance chief and general counsel of Razer Inc., Skullcandy Inc. and BitTorrent.

Shares of Overstock.com, which have added 33% over the past three months, were inactive premarket.

Write to Anne Steele at Anne.Steele@wsj.com