medicine's long tail, where every patient is basically their own clinical trial.
means a condition affecting a small enough population that research, diagnosis, and treatment all lag far behind common illnesses.
from defined by law, not biology: the US Orphan Drug Act of 1983 set the threshold at fewer than 200,000 patients nationwide, because drugmakers had no financial reason to chase diseases too small to profit from.
progeria — causes rapid aging in children, roughly 400 known cases worldwide
huntington's disease — genetic, fatal, affects about 3 to 7 per 100,000 of european descent
cystic fibrosis — once fatal in childhood, now median survival past 50 in the US
pompe disease — muscle-wasting disorder that inspired the film extraordinary measures, 2010