(Reuters) - Hewlett-Packard Co (N:HPQ) said interim Chairman Ralph Whitworth resigned from its board of directors, effective Wednesday, to focus on his health.
Whitworth, who runs activist hedge fund Relational Investors LLC, joined HP's board in 2011. He was appointed HP's interim chairman in April last year.
It was not immediately clear what illness Whitworth, 58, was suffering from.
Relational Investors said co-founder Whitworth was taking a leave of absence from the hedge fund and it wished "his family all the best at this difficult time."
"Out of respect for Ralph's privacy, the firm is not providing any additional information," Relational Investors said in a statement.
Relational Investors owned 1.49 percent stake in HP as of March 31 and is among the technology company's top ten shareholders, according to Thomson Reuters data.
Apart from HP, Whitworth has served on the boards of 11 public companies, including Genzyme Corp [SASYGE.UL], Mattel Inc (O:MAT) and Waste Management Inc (N:WM).
HP's board will discuss the appointment of a new chairman at its next meeting, the company said in a statement.
HP's shares were down slightly at $34.04 in premarket trading on Tuesday. The stock has risen more than 60 percent since Whitworth became interim chairman.
(Reporting by Supantha Mukherjee in Bangalore; Editing by Kirti Pandey)