Trying to find a book

[Avenkal]

Hi sorry if this is vague my mom is looking for a book and this is the best place i could think of to find it. Ok she described it to me as a post apocaliptic book where the charicters get exposed to radiation. Due to being exposed they start to form these crusty balls around their head. When the balls crack open their true inner being is exposed. She thinks it was called sara's song or somthing along those lines. I apreceate any help i can get and appoligize for my spelling.

[stePH]

That would be Swan Song by Robert McCammon.  I quite liked it, despite it being a blatant imitation of Stephen King's The Stand ... in fact, I'd be hard pressed to say which book I liked better.