Matthew Deffebach returned to his labor and employment practice at Haynes and Boone in Houston on Monday, about a month after the 39-year-old partner donated a kidney to the son of Iva York, a longtime staffer at the firm. The date of Deffebach’s return is particularly fitting because it was the start of National Kidney Awareness Month.

Deffebach donated one of his two healthy kidneys to Mitch York, who had been on the kidney transplant list for more than three years, and was facing imminent dialysis late last fall because his kidneys were functioning at a 6 percent level. Mitch York was diagnosed with Berger’s disease, a rare illness that can cause renal failure.