CASE REPORT
A 65 years old Caucasian man with a past medical history
of degenerative disc disease (DDD), chronic neck
and low back pain, asthma, food and latex allergy,
constipation, major depressive disorder (MDD), and post-traumatic
stress disorder (PTSD) presented to dermatology clinic
with a seven-month history of pruritus and “rash†on the
neck. He stated that his pruritus started five days after he had
onabotulinumtoxinA treatment in his neck and upper back for
myofascial pain. He had pre-existing muscular pain from the
neck down to inferior angle of scapula, and his physical medicine
& rehabilitation (PM&R) physician performed onabotulinumtoxinA
injections to the bilateral trapezius, rhomboid,
cervical paraspinals, supraspinatus, and infraspinatus muscles
to alleviate the neuromuscular pain in these areas. The
injections included a total of 100 unit of onabotulinumtoxinA
diluted in 5cc normal saline. His medications on presentation
in dermatology clinic included morphine, methocarbamol,
fluticasone, budesonide, ipratropium bromide, loratadine,
cholecalciferol, quetiapine, fluoxetine, pantoprazole, polyethylene
glycol, and docusate. Physical examination revealed
linear, atrophic plaques, and hypopigmented, linear patches
on the dorsal neck bilaterally with overlying excoriations. The
diagnosis of pruritus associated with onabotulinumtoxinA
treatment was made due to the temporal relationship. The patient
was prescribed oral hydroxyzine, mupirocin (Bactroban)
ointment, and camphor & menthol (Sarna®) lotion.
The patient returned to dermatology clinic three weeks later
for follow-up and reported complete resolution of his pruritus
since day 2 of treatment, and has stopped scratching the neck
with significant healing of excoriations (Figure 1). His neck pain
was still present at this visit.
DISCUSSION
We present this interesting case as we did not find other instances
of pruritus associated with onabotulinumtoxinA treatment in
the medical literature. OnabotulinumtoxinA is a neurotoxin that
targets pre-synaptic axon terminals and inhibits acetylcholine
secretion and results in muscle weakness. OnabotulinumtoxinA
is FDA approved for medical treatment of strabismus and
blepharospasm (1989), cervical dystonia (2000), and for cosmetic
improvement of glabella lines (2002), and crow’s feet (2013).
OnabotulinumtoxinA is one of the most widely used agents today
for cosmetic treatments. According to the American Society
for Dermatologic Surgery (ASDS), there were 1.8 million cases
of wrinkle-relaxing injections (such as onabotulinumtoxinA) performed
in 2013.1 This was a 20% increase from 2012.
Additionally, physicians have been using onabotulinumtoxinA
for off-labeled treatments. Some of the off-labeled uses of onabotulinumtoxinA
include treatment of neuromuscular pain,
neurogenic overactive bladder, chronic migraines, hyperhidrosis
and gustatory sweating syndrome, achalasia, and anal
fissure.2 OnabotulinumtoxinA is generally considered a safe
medication and is associated with rare serious adverse effects.
In one study, serious adverse events were more likely to be
associated with therapeutic uses than with cosmetic uses.7
Common adverse effects after cosmetic uses include lack of intended
cosmetic effect, injection site reactions, ptosis, muscle
weakness, and headache. Based upon a PubMed search and review
of the literature combined with clinical experience, to our
knowledge, there are no previously reported cases of pruritus
after onabotulinumtoxinA treatment. The pruritus for our patient,
compared with common side effects, was not transient in
nature. There is a possibility that the patient’s presentation may
have been an unmasking or precipitation of herpes zoster with
