Mudblood Malfoy

What will happen when Lucius lets slip to the dark lord that the great Lucius Malfoy is a mudblood?? Muggle born and ashamed. The malfoys are banished to live amongst muggles, but what does this mean for Draco? Or Narcissa? Sirius steps in as a hero, possbly. And has bellatrix always been so comfortable with Snape?