Clinical resistance to three types of botulinum toxin type A in aesthetic medicine.

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.