The syndrome has been hypothesized to be a variant of alopecia areata diffusa or autoimmune non-scarring hair loss that selectively affects all pigmented hairs, leaving only the white hair behind. Marie Antoinette syndrome is caused by high levels of emotional stress, which, in turn, causes less pigmentation of the hair. These form the basis of most uses of the idea in fictional works. It has been found that some hairs can become colored again when stress is reduced. One study with experiments on mice found that stress caused white hair even if the immune system was suppressed (ruling out auto-immune response) and if the glands producing cortisol were removed. The study concluded that over-activation of the sympathetic nervous system was causing stem cells to stop producing pigment cells in hair follicles.
Canities subita
The Fountain of Age
Blind man of Bethsaida
MedCity 
Black Death migration
Juven
Plague doctor costume
Biovail