Also, back to your original Q about PTSD v IED ...
A lot of diagnosis in the DSM-V share symptoms.
Just because explosive rage can be a symptom of PTSD, doesn't mean you have every other Dx that also has explosive rage & in it. Although it doesn't exclude co-occurring disorders.
Like a fever of 104 can be attached to a lot of different illnesses, or blown pupils can be illness, trauma, or drugs... Or you can pick someone up in hypoglycemic shock, who has ALSO knocked themselves hard enough to be unconscious in a car wreck. Course, that one, the depressed fracture on her noggin gets the blame off the bat, when it was probably secondary. Neurology/psychology isn't all that different from the rest of medicine.
There's usually a difference, even in shared symptomology, though. Unlike a fevers a fever, in psych something can look the same, but not just have a different cause, but a different feel to it.
Like I'm ADHD. My peeps tend to be super argumentative/contrary. But we're not ODD (oppositional defiant disorder, who argue with every damn thing). Tell someone with ODD that the sky is blue, and they'll say no it isn't... just to say no. Tell someone with ADHD the sky is blue, and they might say "no" too, but if you press them you'll end up with a whole Bubba Gump Shrimp list of all the times when the sky is not blue (at night, dawn, sunset, in storms, cloud cover, smoke cover, on Jupiter, in black and white movies, if all the water got sucked out kill other color spectrum, if, if, if, if, if etc.). The ODD brain locks onto the inverse and shuts everything else out. The ADHD brain starts spinning out looking for all the possible exceptions. Even though our moths might say the same thing / it looks the same at first glance.
So now I'm co-occurring ADHD + PTSD. Both can make the other worse, hide symptoms, help out, or have no effect whatsoever. Who knows, maybe you're IED + PTSD. But ADHD, Bipolar Disorder, Aspies, Sensory Processing Disorder, and a half a dozen other disorders off the top of my head all come along with periodic meltdowns.