Thirteen-term Rep. Robert T. Matsui (search) died Saturday night after complications from a rare stem cell disorder. A Democrat from California, Matsui was 63.

Matsui entered Bethesda Naval Hospital on Christmas Eve suffering from pneumonia, one of several illnesses that can occur as a result of Myelodysplastic Syndrome (search), a stem cell disorder that causes an inability of the bone marrow to produce red blood cells, white blood cells and platelets.

"In his 26 years in the United States House of Representatives, Bob Matsui was a champion to preserve Social Security (search), a crusader for economic justice, and a fighter for all of America’s children. It is with great sorrow that I join our constituents in California and colleagues in Congress to mourn the loss of a dear friend, respected leader, and dedicated family man," said House Minority Leader Nancy Pelosi, D-Calif.

"Bob Matsui was a dedicated public servant and a good and decent man who served with distinction and integrity in the U.S. House of Representatives for more than 25 years. In the Congress, he was a leader of his party admired by colleagues on both sides of the aisle," President Bush said in a written statement.

Matsui, who was vice mayor of Sacramento when he first campaigned for congressional office in 1978, was a senior member of the House Ways and Means Committee, and committed himself to tax, international trade, Social Security, health care and welfare reform issues. As the top Democrat on the Social Security Subcommittee, he was the leading Democrat proposing incremental revisions to Social Security, the social insurance program for America's seniors, and was the voice of the party in opposing Bush's plan to allow young workers the option of personally investing a portion of their payments into the system.

Bush "wants to use an ideological solution to a manageable problem," Matsui said last month.

Matsui, who was also a Democratic whip at-large, was one of the key Democrats who helped former President Clinton win passage of the North American Free Trade Agreement (search), the establishment of the World Trade Organization (search) and the Permanent Normal Trade Relations with China (search). More recently, Matsui had pushed for environmental protections and the provision of fair compensation in all trade deals.

Matsui was also known for his commitment to American children. He has worked on child welfare reform to expand assistance to at-risk children, introduced legislation to strengthen enforcement of child support payments and helped craft the foundation for the State Children's Health Insurance Program (search), which helps low-income children with medical coverage.

"Bob Matsui was one of the toughest and most morally principled people in public service. His vision of fairness and principle for how to take care of the disadvantaged and poor was unparalleled in the political arena. His vision of right and wrong always guided him in the complex and politically challenging policy fights in Congress over welfare reform, taxes, pensions, and Social Security -- issues in which he was a recognized leader," said Rep. George Miller, D-Calif.

"As Congress prepares again this year to consider reforms to Social Security and our tax system, it is not overstatement to say that Bob's expertise and experience on these issues are virtually irreplaceable. His leadership will be sorely missed," said House Minority Whip Steny Hoyer, D-Md.

Matsui, who last session was chairman of the Democratic Congressional Campaign Committee (search), the fund-raising arm for House Democrats, held a reliably liberal record. He supported a woman's right to an abortion, opposed a ban on partial birth abortions and backed a constitutional amendment to ensure equal rights by gender. He supported gay adoptions, campaign finance reforms and easing immigrant residency rules.

He opposed making Bush's tax cuts permanent and did not vote for getting rid of the estate tax. He did, however, back making the marriage penalty tax reduction permanent. Matsui opposed school vouchers for children in failing schools, a ban on human cloning, oil drilling in the Arctic National Wildlife Refuge in Alaska, the death penalty and three strikes law for repeat offenders. He also opposed a ban on liability payments for medical lawsuits. He opposed the war in Iraq, but backed the $87 billion emergency spending bill to pay for troops.

An attorney before joining Sacramento's city council in 1971, Matsui, a third-generation Japanese-American, was six months old when he and his family were taken from Sacramento and interned by the U.S. government at the Tule Lake camp (search) in 1942, after Japan's attack on Pearl Harbor.

In 1988, he helped pass the Japanese-American Redress Act (search) through Congress, in which the government formally apologized for the World War II internment program and compensated victims. He also sponsored bills to establish memorials in Los Angeles and Washington, D.C. as a symbol of Japanese-American patriotism.

Matsui was survived by his wife Doris, his son Brian, daughter-in-law Amy and granddaughter Anna. The family is establishing a charitable fund in memory of the congressman. Gifts can be sent to The Matsui Foundation for Public Service, P.O. Box 1347, Sacramento, Calif. 95812.

A special election will be held to replace Matsui, who won his 14th term with 71 percent of the vote. An election could come in early spring. In the meantime, the clerk of the House will operate the District 5 California office.