Apple's Steve Jobs Takes Medical Leave Again

Updated 1:49 p.m. ET

Apple Inc. CEO Steve Jobs is taking his second medical leave of absence in two years, raising serious questions about his health and the leadership of a company at the forefront of a personal computing revolution.

Apple did not provide any further information about Jobs' current condition, including whether Jobs is acutely ill, whether the leave is related to his 2009 liver transplant or whether he is at home or in a hospital.

Apple spokesman Steve Dowling referred to the text of Jobs' note to employees, which was made public Monday. (Read the message in full below.)

In the note, Jobs, 55, said he will continue as CEO and be involved in major decisions. As has been the case during past illnesses, Jobs said chief operating officer Tim Cook to be responsible for all day-to-day operations.

"I love Apple so much and hope to be back as soon as I can," Jobs wrote. "In the meantime, my family and I would deeply appreciate respect for our privacy."

It's not clear how investors will react to the news, but Apple has fallen sharply in response to medical news and rumors about Jobs in the past. Apple's shares plunged 6.4 percent in trading Frankfurt to 243.50 euros ($323.73). U.S. markets were closed Monday in observance of Martin Luther King Day.

Apple has a history of extreme secrecy when it comes to the iconic CEO's health, disclosing major illnesses only after the fact.

The company waited until after Jobs underwent surgery in 2004 to treat a very rare form of pancreatic cancer — an islet cell neuroendocrine tumor — before alerting investors. That type of cancer can be cured if diagnosed early, unlike the deadlier and more common adenocarcinoma.

By 2008, Jobs had lost a noticeable amount of weight, but Apple attributed his gaunt appearance to a "common bug." In January 2009, Jobs issued a statement saying the weight loss was caused by a hormone imbalance, and that the treatment was simple. He backtracked a week later, however, announcing a six-month medical leave. During that time, he received a liver transplant that came to light two months after it was performed.

Few CEOs are considered as instrumental to their companies as Jobs has been to Apple since he returned in 1997 after a 12-year hiatus. With Jobs serving as head showman and demanding elegance in product design, Apple has expanded from a niche computer maker to become the dominant producer of portable music players, a huge player in the cell phone business and the inventor, with the iPad, of a new category of modern tablet computers.

"In the short term it's actually not a big deal. Apple has an excellent management team. You can see that manifested in Apple's success - Jobs can't do that alone," said CBS Moneywatch.com executive editor Jack Otter. "I think the big problem is in the long term, Jobs is a visionary and this is a visionary company. It's changed the way we think about personal computers, about smart phones. And you have to wonder, can they keep on hitting it out of the park without a visionary at the helm."

Jobs co-founded Apple with Steve Wozniak in 1976 at the dawn of the personal computer revolution. He was forced from the company in 1985 but returned as CEO in 1997, slashing unprofitable product lines and helping rescue the company from financial ruin.

Some investors fear that without Jobs, Apple would not be able to sustain its growth or its high-end minimalist style, and Apple's shares have surged and crashed over the years with rumors or news about the CEO's health.

Business Insider's Henry Blodget wrote Monday that the wording of Jobs' e-mail to employees was "not encouraging."

Blodget seized particularly on Jobs' declaration that "I love Apple so much and hope to be back as soon as I can."

"In our opinion, those are not the words of someone taking a short leave who is confident he will be back at the company soon (or ever)," Blodget said. "Rather, in our opinion, they read like the tragic, heartfelt sentiments of someone who thinks he might never be coming back."

In 2010, the year that brought the highly anticipated iPad, investors seemed accustomed to Jobs' extreme thinness and focused instead on the early success of the device.

Investors may also have growing faith in Cook, who is seen as a logical successor to Jobs and who took the reins during the two previous health scares. Cook joined Apple in 1998, and ran the Cupertino, Calif.-based company for two months in 2004 while Jobs battled cancer. His performance won him the promotion to chief operating officer in 2005.

Analysts credit Cook with solving problems that Apple was having with inventory management. And under his direction in 2009, the company kept cranking out well-received products including updated laptops with lower entry-level prices and a faster iPhone with many longed-for features.

Jobs' e-mail to employees, in full:

Team,

At my request, the board of directors has granted me a medical leave of absence so I can focus on my health. I will continue as CEO and be involved in major strategic decisions for the company.

I have asked Tim Cook to be responsible for all of Apple's day to day operations. I have great confidence that Tim and the rest of the executive management team will do a terrific job executing the exciting plans we have in place for 2011.

I love Apple so much and hope to be back as soon as I can. In the meantime, my family and I would deeply appreciate respect for our privacy.