Transient Skin Coloration Changes in GDD
I am extremely fond of the cuttlefish. Very intelligent animal. Also probably related, the females play a dominant role in what progeny will be generated - which I think is the mark of animals that evolve in intelligence.
Who does not love and marvel at the dramatic transient pigmentary changes that they can produce... then the whole host of other creatures that express some form of bioluminescence. Until recently, most of these pigmentary effects were not appreciated by humans until advanced science could reveal it.
Turning back to GDD....the durable but changing skin pigmentary changes of hemorrhage are well recognized and their relation to hemoglobin. Also the variety of temperature- related/ allergy-related/ blood flow-related skin color changes are familiar.
What is remarkable with GDD is that a full range of colors may transiently appear in sufferers, from pinks to yellows to blacks - which can be horrifying to everyone, but ofcourse in particular the sufferers themselves. What is remarkable, unlike with bruises, these skin colorations can change and resolve rapidly. Many sufferers have sent me a huge number of photos illustrating this.
My theory is that these reflect chemicals elaborated by certain cells into interstitial tissue, that therefore lasts for some time, but will eventually be cleared by lymphatics or the venous system. We do know, and I have blogged previously, immune cells (and other cells) elaborate perhaps at least 50 cytokines in response to a challenge/threat, but many other molecules: growth hormone, heparin, among them... So it may be we are aware of 100 molecules released... which may mean that they number in the hundreds. That being said- maybe a few of these molecules are pigmentary in nature. As their presence is transient, this would also reflect why they have not been demonstrated histologically (unlike CD34+ circulating fibrocytes in NSF).
If this is the case, then which cells would elaborate them? A leading candidate would be the Langerhans cells, immune cels dwelling in the skin tissues. If the coloration molecules do exist, what would be the purpose? Probably similar reasons as coloration molecules in other creatures. As they occur in GDD, their evolutionary purpose may have been to alert prohominids that whatever they just were in contact with, by breathing, touch, or consumption, was dangerous, and the indicator was transient skin coloration.
As a side note, the transient nature of the coloration has to the present time been used by skeptics that this finding never happened, because it was not present when they saw the sufferer.
I want to emphasize this is an opinion and not proven fact, but an intriguing possibility: a family of coloration molecules in humans, as observed in cuttle fish. There are other skin conditions that this transient coloration has been observed in.