This writer talks about 13 different kinds of fatigue she experiences with Sjogren's Syndrome - an autoimmune disease. I'll bet that other autoimmune diseases produce similar kinds of fatigue. Several of them are the same type of fatigue found in ME/CFS and FM.
What she calls "Rebound Fatigue" appears to be a lesser form of post-exertional malaise
There's also brain-fog and the heavy legs feeling. She does not say flu-like fatigue but these are so close to ME/CFS that I imagine you could distinguish between the two diseases using symptoms of fatigue! Maybe the degree of fatigue would help...
Tired-wired (Wired Tired)
Tired-wired is a feeling that comes from certain medications, such as prednisone, too much caffeine, or too much excitement or perhaps it is just a function of Sjögren’s. My body is tired but my mind wants to keep going and won’t let my body rest.
What she calls "Rebound Fatigue" appears to be a lesser form of post-exertional malaise
Rebound fatigue
If I push myself too far and ignore the cues my body is sending me to stop and rest, my body will fight back. When I do more than I should, the result is an immobilizing fatigue. It comes on after the fact, i.e., do too much one day and feel it the next. If I push myself today, I very likely will have to cancel everything tomorrow. An extended period of doing more than I should will almost certainly cause a flare.
There's also brain-fog and the heavy legs feeling. She does not say flu-like fatigue but these are so close to ME/CFS that I imagine you could distinguish between the two diseases using symptoms of fatigue! Maybe the degree of fatigue would help...