Source : WordNet®

followup
     n 1: a piece of work that exploits or builds on earlier work;
          "his new software is a follow-up to the programs they
          started with" [syn: {follow-up}]
     2: an activity that continues something that has already begun
        or that repeats something that has already been done [syn:
         {follow-up}]
     3: a subsequent examination of a patient for the purpose of
        monitoring earlier treatment [syn: {follow-up}, {reexamination},
         {review}]

Source : Free On-Line Dictionary of Computing

followup
     
        On {Usenet}, a {posting} generated in response to another
        posting (as opposed to a {reply}, which goes by e-mail rather
        than being broadcast).  Followups include the ID of the
        {parent message} in their headers; smart news-readers can use
        this information to present {Usenet} news in "conversation"
        sequence rather than order-of-arrival.  See {thread}.
     
        [{Jargon File}]