Journal of Cosmetic Dermatology, 13, 346--348 Clinical resistance to three types of botulinum toxin type A in aesthetic medicine Farid Stephan, MD, Maya Habre, MD, & Roland Tomb, MD, PhD Faculty of Medicine, Saint Joseph University, Beirut, Lebanon Summary Botulinum toxin injections have become the most frequent noninvasive cosmetic procedure carried out worldwide. Botulinum toxin has also multiple other indications in different medical fields. However, with the repetition of injections, a new concern has emerged: clinical resistance and loss of effectiveness of the treatment. After reporting a case of primary nonresponsiveness to three types of botulinum toxin type A injections, we conducted a review about all factors leading to the primary or secondary nonresponsiveness, as well as the factors affecting the immunogenicity of this neurotoxin. Most of the reports and studies focused on secondary resistance to botulinum toxin (BT) and the neurotoxin immunogenicity; primary nonresponsiveness was rarely reported. Factors leading to primary or secondary resistance to BT injections were numerous. In the majority of the studies, development of neutralizing antibodies to botulinum toxin was considered responsible of the induced clinical resistance. Patients should be aware of this rising concern as well as clinicians who should learn how to minimize the risk of resistance development, sparing the patients more invasive treatment modalities. Further studies related to botulinum toxin resistance are needed. Keywords: resistance, botulinum toxin type A, incobotulinumtoxinA, abobotulinumtoxinA, onabotulinumtoxinA Abbreviations BT botulinum toxin MPA mouse protection assay nAB neutralizing antibodies Introduction In this era, botulinum toxin (BT) has become a primor- dial key in facial rejuvenation. It is a minimally inva- sive procedure that revolutionized cosmetic field worldwide. After more than 20 years of use of BT, sec- ondary resistance for an esthetic application was rarely reported in the literature. We report a case of a pri- mary clinical resistance to three types of BT type A in the treatment of facial rhytides. Case report Our patient is a 51-year old otherwise healthy woman who presented to our clinic in May 2013 for the treat- ment of the upper face wrinkles with BT. She had already received three cycles of BT injec- tions (onabotulinumtoxinA Botox â ; Allergan Inc, Irvine, CA, USA and abobotulinumtoxinA, Dysport â ; Ipsen Limited, Slough, UK) since 2011 to the forehead, glabella, and crow’s feet areas. She experienced partial Correspondence: Maya Habre, Dermatology department, Hotel Dieu de France Hospital, Alfred Naccache Street, Achrafieh, PO Box 166830, Beirut, Lebanon. E-mail: maya.habre@gmail.com Accepted for publication April 19, 2014 346 © 2014 Wiley Periodicals, Inc. Parting Thought