Raynaud's syndrome is where the extremities such as fingers and toes turn purple from lack of circulation. My sister has the condition, so I've been able to see it firsthand. The differences with my symptom is that the skin of my fingers and toes never changes color, just the nails, and secondly my temoperature plunges to borderline hypothermia, whereas with raynaud's syntrome as I understand it there is no change in body temperature.
I have Raynaud's syndrome which causes my nails to turn blue when cold (but "cold" is not really all that cold to healthy people). I was told it can be a part of ME/CFS. When my hands and feet warm up they turn a purplish red, swell, get itchy, and sting. My body temperature is always (oddly) at a low-grade fever (99-101.5 F). However, my hands and feet are at least 30 degrees less then my body temperature. I have a doctor who is obsessed with this symptom and he always measures my hand temperature which is the only reason I know about the temp. difference.
On the other hand, sometimes I think that ME/CFS is a kind of premature aging disease. I have several friends in their 80's who have more stamina and mental clarity than I do. So maybe nail ridges go along with that.
Sorry, I know this is off topic, but I agree that people who have ME age more quickly. I started getting lots of age spots in my late 20's. They are genetic but my parents didn't get them until their late 50's. I do think our bodies are aging more quickly due to this disease. Perhaps other diseases do the same but I think, in my very non-scientific opinion, that there is a link.