What would cause a young man to have white hair?

White hair. If your mother or father's hair turned white at an early age, you may be genetically programmed for premature graying. Your genes determine when production of melanin stops, and your dna may destine you to platinum hair at an early age.
Usually genetics. Graying / whitening of hair is related to genetic predisposition. Age of initial graying is largely a matter of genetics. However stressors: nutritional deficiencies, chemotherapy, traumatic head injuries, low vitamin B levels, zinc deficiency, severe illness, surgery & marked emotional stress may impact earlier depigmentation in people who are already predisposed to gray/ white hair.