I don't think it is, but I'm at the end of my tether and just want to get some perspective on this.
DS1 threw a tantrum this morning at his grandparents before leaving for school because he remembered he'd left his toy leopard at home. There was no way of getting it because DH and I were on our way to work, so DS1 threw himself on the floor and howled, continued howling on the way to school, and had to be prised, still kicking and screaming, from my MIL by the headmaster, and dragged into the playground.
DS1 does this kind of thing at least once or twice a day when he doesn't get his way about something, or is disappointed, or has to wait, even though we've always made it clear that tantrums aren't the way to get what he wants. If he doesn't throw a tantrum he whinges and whines until I feel like throwing one.
None of his friends of the same age seem to do this, and nothing can get him out of a tantrum once he's in it - we ignore him, give him time out, try to understand - and he doesn't seem to be growing out of it. His brother who has just turned three doesn't throw tantrums like this, so DS1's behaviour seems particularly excessive to me.
Sorry for the long-winded post but I'm beginning to be afraid there's something wrong with him. Or us.