Pyomyositis is an acute, deep skeletal muscle infection
seen especially in Africa and South Pacific.
2,15,16 The
exact etiology is not clear. It can occur in any age group,
although it is more common in the first and second
decades of life.
17
Bacterial infection is rare in the skeletal muscle,
which is usually resistant to infection.7,8,18 It has been suggested that in order for PM to develop,
some alterations in the usual defenses of the affected
muscle are necessary. Trauma has been postulated
to contribute to PM by facilitating hematogenous
access to the muscle tissue and by providing an
iron-enriched environment for bacterial growth
through the release of myoglobin.7,18 The source of
the bacterial inoculum is believed to be either from
distant skin infections with transient bacteriemia
or, less commonly, from local vascular or lymphatic
contamination.4,7,18,19 Children seldom have preexisting
conditions compared with adults.2,10,16,20 In
the paper by Unnikrishnan et al.17 only two of 13
pediatric patients with PM had any pre-existing
medical problems (asthma, juvenile arthritis), and
these were not directly linked to PM. The association
of trauma at the time of bacteriemia has been
postulated to explain the increased risk of developing
pyomyositis.17 Our patient also had a suspicious
trauma history. It has been reported that S. aureus is
the most common pathogen in PM.4,7,18 This was the
same microorganism isolated from the pus material
of our patient. Because of his chronic abdominal pain,
we investigated the colon regarding IBD, a probable
cause of PM, but the colonoscopy results were normal.
Therefore, a definite etiology could not be identified
in this patient.
Pyomyositis usually occurs in proximal muscle
groups, including the quadriceps, iliopsoas, gluteus,
calf, shoulder, and upper arm muscles. either in single
form or in multiple groups.4,7,18 Our case presented
with gluteal localization of PM, which is reported
frequently in the involved area.
Three clinical stages of PM have been described.1,17,18
In the early invasive stage, pain and mild swelling of
the involved muscles are the first signs of PM. Because
the muscle abscess is contained by overlying fascia,
local erythema and heat may be minimal until days
or even weeks after symptom onset. Localized signs
and symptoms can precede systemic manifestation by
weeks. Next, the suppurative stage occurs 10-21 days
after symptom onset and includes fever, malaise,
leukocytosis, elevated ESR, and anemia. In this
stage, the affected muscles become very tender and
edematous. After abscess formation, the involved
muscles typically become fluctuant. If the infection
is not recognized and treated in this stage, PM can
progress to the third septicemic stage. Toxicity and
bacteriemia are found in this last stage along with
the formation of metastatic abscesses, and abscess
complications such as septic shock, endocarditis,
myocarditis, pericarditis, pneumonia, lung and
brain abscess, renal failure, rhabdomyolysis, and
compartment syndrome may develop.1,4,7,18
The potential complications are secondary to
delayed presentation. The vast majority of patients
show excellent and complete recovery with no longterm
complications.17 However, it has been determined
that most of PM patients present during the suppurative
stage.4,17,18
Although approximately 90% of PM patients present
during the suppurative stage, our patient presented
in the first stage.4,18 However, the opportunity for
early diagnosis was missed, and the delay resulted in
the contiguous osteomyelitis. It has been previously
suggested that CT scans and MRIs are useful imaging
techniques for early diagnosis of PM instead of relying
solely on X-rays.18,21 We believe the complication in
our case could have been prevented if an MRI had been
performed earlier. Treatment with antibiotics alone may
be sufficient in the first stage of PM,4,8 but the delay in
diagnosis in our case probably resulted in the abscess
drainage and osteomyelitis complication.
We conclude that early diagnosis, established via
an MRI or CT scan, prompt drainage of any abscess,
microbiological studies, and appropriate intravenous
antibiotic treatment provide successful management of
PM in children.
Declaration of conflicting interests
The authors declared no conflicts of interest with
respect to the authorship and/or publication of this
article.
Funding
The authors received no financial support for the
research and/or authorship of this article.
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