Representative Steve Scalise, Republican of Louisiana and the majority leader, said Tuesday he had been diagnosed with a rare form of blood cancer but planned to return to Washington to continue working as he undergoes treatment over the next several months.
Mr. Scalise, 57, said in a statement that he had begun treatment for multiple myeloma, which he described as “a very treatable blood cancer,” after feeling ill over the August congressional recess and having tests that led to his diagnosis.
It came at a critical moment for Mr. Scalise, who is known for his ability to speak to the hard-right faction of the fractured Republican conference and has a pivotal role to play in the House in the coming months, with Congress facing the possibility of a government shutdown on Oct. 1. Lawmakers remain far from reaching any agreement on spending levels that would keep the government running on a long-term basis. The House left Washington last month for a six-week summer recess nowhere near a deal on 11 of the 12 appropriations bills that still must be passed, hamstrung by internal divisions over spending and social issues.
Mr. Scalise, who previously served as the Republican whip, is expected to play a crucial role in negotiating with members of the ultraconservative House Freedom Caucus, who are threatening to force a shutdown unless their priorities are addressed.
The diagnosis was only the latest setback for Mr. Scalise, who was gravely wounded in 2017 when a gunman opened fire on members of the Republican congressional baseball team at a practice field in Alexandria, Va. He was shot in the hip and underwent many surgeries to relearn how to walk, regaining almost full mobility.
“I am incredibly grateful we were able to detect this early and that this cancer is treatable,” Mr. Scalise said in a statement on Tuesday. “I will tackle this with the same strength and energy as I have tackled past challenges.”
Speaker Kevin McCarthy, who has had a strained relationship with Mr. Scalise, said in a statement that he had spoken with his No. 2 on Tuesday and found him to be in good spirits.
“Nothing — not a gunshot wound and certainly not cancer — will stop him from accomplishing what he sets his mind to,” Mr. McCarthy, the California Republican, said in a statement.
In multiple myeloma, certain healthy blood cells become cancerous, throwing off abnormal proteins that can cause problems and crowding out cells needed to fight infections.
A relatively uncommon cancer, it is estimated to be diagnosed in about 35,000 people in the United States annually, more often affecting men and Black people. About 60 percent of patients diagnosed with multiple myeloma in recent years survived the effects of their cancer for at least five years, though the survival rate depends on how far the cancer has spread.
Patients can face more frequent infections and bone and kidney problems, but there are a number of treatment options that depend on how quickly the cancer is growing. Those include immunotherapy, which helps the body’s immune system attack cancer cells, chemotherapy and corticosteroids.
Some patients are also candidates for a stem cell transplant. Drug treatment is first used to reduce the number of cancerous cells in the body and then unhealthy blood-forming stem cells are replaced by healthy ones.
On Tuesday, Republicans were quick to offer Mr. Scalise their public support and highlight his resilience.
“Steve is as tough and kind as they come, and he has beaten so many unbeatable odds,” Representative Elise Stefanik, Republican of New York, said in a statement. “We know he will fight this next battle with that same resolve.”
“Steve is a fighter, and we stand with him as he enters this latest battle,” Representative Patrick T. McHenry, Republican of North Carolina, said in a statement.