orphan disease
n.— «A 12-year-old Simi Valley boy with a rare immune system disorder has inspired a series of benefits to help find a cure for what is known as an “orphan disease” because it affects too few children to warrant federal research funds.» —“Simi boy’s rare disease inspires annual fundraising softball tournament” by Alicia Doyle Ventura County Star (California) June 23, 2008. (source: Double-Tongued Dictionary)
Further reading
Understanding the varieties of conversational styles can mean the difference between feeling you’re understood and being insulted. “High-involvement” speakers interrupt or talk along with someone else to signal their enthusiasm...
An anadrome is a word that forms a whole new word when you spell it backwards. For example, the word “stressed” spelled backwards is “desserts.” Some people’s first names are anadromes. There’s the girl named Noel...
this term is related to the term “orphan drug”, which has been in common use for at least thirty years. Indeed it appears in my 25thEd (1990) Stedman’s, under orphan products: “drugs, biologicals, and medical devices… that may be useful in common or rare diseases, but which are not considered commercially viable.” The FDA has a special status for these drugs, which are usually used to treat, you guessed it, orphan diseases.