# Botulinum toxin: a new differential diagnosis for a lytic bone lesion

## TL;DR

A woman developed a bone lesion after a Botox injection, suggesting it could be a rare side effect of the treatment.

## Contribution

This is the first reported case linking Botox injections to lytic bone lesions.

## Key findings

- A 62-year-old woman developed a lytic lesion in her frontal bone after a Botox injection.
- No neoplastic cause was found, and the lesion was likely due to Botox entering the bone cortex.
- This case highlights a new differential diagnosis for isolated lytic bone lesions post-Botox.

## Abstract

Botulinum toxin, produced by the Gram-positive anaerobe Clostridium botulinum, is composed of seven antigenic subtypes (A, B, C, D, E, F, and G). Currently, only Botulinum toxin type A, commonly referred to as “Botox,” is approved for clinical use, given its relatively safe clinical profile. Botulinum toxin type A has a wide range of therapeutic indications, including treatment for dystonia, migraine headache, neurogenic bladder, and large muscle spastic disorders. However, the toxin is most widely known for its cosmetic effects in treating wrinkles and facial lines.

This article describes a 62-year-old Caucasian female who presented for investigation and workup of an isolated lytic lesion of her frontal bone a few weeks after administration of botulinum toxin injection into the corresponding site in the frontalis muscle. This presented as a large, palpable, painless forehead lump causing significant psychological distress. After no neoplastic cause for the lesion was found and histopathology was performed, our researchers concluded that the most likely explanation was that the bony lytic lesion resulted from inadvertent injection of the “Botox” neurotoxin through the intended target muscle and into the cortex of the underlying bone.

Our search of the literature failed to identify any previous cases of this occurring. However, as the popularity of this cosmetic procedure only increases, we believe that this represents an important possible differential for isolated lytic lesion after administration of “Botox” injection.