Answer to Medical Challenge-Yellow Nail Syndrome

Yesterday's Medical Challenge answer was clear to some readers and a mystery to others.  The answer was:
#4  Yellow Nail Syndrome.  Although nails can become discolored from nail polish, the medical Yellow Nail Syndrome is a sign of a serious disorder and not well understood.  It is believed to be associated with  restrictive lung disease or  (rarely) problems with lymphatic drainage channels.