Well, I am just too curious. My dad has it and so do I. He says it is hereditary and he's been having it from his childhood as well. I also have these lumps from early childhood so far I remember. Mostly the lumps are in the arm muscles. and some in my thighs, and around my stomach. The lumps seems to grow these days. I don't know what does it account for but maybe, with my growth, the lumps are growing too. I am 21 years old and I used to be a little thin. Now I am gaining weight and the lumps in my arms seems conspicious. What should I do?