Buried in a frustrating article on Amish health-care:
The next year, the couple had a second son, Henry. He was diagnosed with a disorder called maple syrup urine disease, in which patients can't break down certain amino acids. High levels of these amino acids in the blood can cause brain damage and death.
Wikipedia » Maple Syrup Urine Disease:
Characterized by the presence of sweet-smelling urine, with an odor similar to that of maple syrup.
I wonder if it would be possible to induce MSUD in homeless people.