Horizontal animation deformity as unusual complication of neurotoxin modulation of the gummy smile

Injections  of  botulinum  toxin  type  A  represent  the  most    common    nonsurgical    cosmetic    treatment    worldwide.  The  authors  report  a  case  of  dynamic  horizontal  wrinkling  in  the  upper  lip  that  appeared  after   botulinum   toxin   type   A   injections   to   treat   gummy    smile    associated    with    nasal    alar    base    reduction,  in  a  28-year-old  woman.  The  anatomic  features and pathogenic mechanism underlying this unusual complication are analyzed and discussed.