My son has a strange condition. For the last year the veins in his left arm may suddenly bulge. The veins will protrude and may hurt. One place, just above his wrist it can protrude up to half an inch. On the inside of his arm the veins really stand out. Sometimes they hurt, sometimes the arm feel weird and heavy. The condition used to happen in both arms. My son is 14, very active and eats normally. It is difficult determing a pattern of when it happens, and he is inclined to say its random. It may occur when working out, playing sport or when waking in the morning.