I've had vitiligo and some hyperpigmented spots for a while and even participated in a study of it. My dermatologist claims it is an autoimmune skin condition, while other docs have had differing points of view. From my own experience, there seems to be two patterns the vitiligo can form in--motheaten patches possibly with darker spots nearby or big wide white pigmentless and sometimes hairless patches. People I have known with the big solid patches often posted that they benefitted from vitiligo treatments to repigment, while I, having the motheaten sort of lots of smaller white spots with some dark spots, did not.
A good friend developed vitiligo on his face and it was due to a pinched nerve in his neck, he underwent neck surgery and spontaneously got better. I saw him before the vit, before the surgery, and after. I got back surgery on my lumbar spine and both my legs repigmented some, so I think in my case there was a circulatory or nerve part to it. But that may not be true because my hypothyroidism went away at the same time, so it may have been due to endocrine.
I have it on the joints of my hands and wrists, where I have arthritis, and under my arms, behind my knees, etc. and my lymph nodes in these areas often swell or are disfunctional by now.
My Mayo hepatologists remarked that they felt I had the vitiligo characteristic of adrenal disease, esp. with the dark patches, dark spots are not vitiligo. They felt my adrenals where harmed by TB and they treated me for latent TB. Its possible that contributed to the improvement in my thyroid.
I can say that I have scleroderma changes on my forearms, psoriatic arthritis in my elbows and knees, rheumatoid changes in my fingers. I guess that's mixed connective tissue disease. I also have liver problems, which can affect not just the metabolism of things you eat or drink, but stuff inside you too I imagine, like hormones.
Hair dye is really bad for it. I use an herbal hair color since alot of my hair is white from vit and disease and raising kids!