Keywords
pyomyositis - staphylococcus aureus - histiocytic necrotizing lymphadenitis
Introduction
Primary pyomyositis is a deep bacterial infection of the skeletal muscle, and it commonly
manifests as a local abscess. It can affect people of any age, but is most common
in the first and second decades of life, with a higher incidence among males. Any
muscle can be affected, but the disease is more frequent in large muscle groups located
around the pelvic girdle and lower limbs.[1]
[2] The diagnosis is often delayed because of its rarity, nonspecific clinical presentation,
and involvement of muscles located in deep compartments. It is typically subacute,
and the patient seeks treatment within an average of 5 to 6 days following the onset
of symptoms.[2] In most cases, the patient presents with fever, pain in the affected region, and
leukocytosis. The diagnosis is usually established using magnetic resonance imaging
(MRI) and confirmed using histopathological examination. The treatment occurs according
to the stage in which the infection is diagnosed.[2]
The present study presents a case of piriformis muscle pyomyositis in a patient diagnosed
with necrotizing lymphadenitis, also known as Kikuchi–Fujimoto disease (KFD). The
Ethics Committee at Hospital Madre Teresa, Belo Horizonte, MG, Brazil approved this
study, and written informed consent was obtained from the family of the patient prior
to her inclusion in the present study.
Case Presentation
A 23-year-old female presented to the emergency department with septic shock secondary
to a respiratory tract infection and was admitted to the intensive care unit (ICU).
She had a history of fever, a poor overall condition, and weight loss over a preceding
period of 2 months. Clinically, in addition to the respiratory distress, there was
evidence of cervical lymphadenopathy and hepatosplenomegaly. She had no significant
past medical history apart from hypothyroidism. The patient reported an absence of
other comorbidities or travel to other countries. She was treated for a lung infection
and discharged with a diagnosis of Kikuchi–Fujimoto disease (KFD) after a lymph node
biopsy. After 30 days, the patient presented with complaints of a deep left gluteal
pain. The patient was then referred to the orthopedic department.
In the orthopedic consultation, the patient reported mild pain in the deep gluteal
region. Upon examination, the patient was afebrile, with an atypical gait, pain upon
palpation of the deep left gluteal region, and no neurological deficits. The left
hip exhibited a mild limitation of motion: 110∘ flexion, 20∘ extension, 40∘ abduction,
20∘ adduction, 30∘ internal rotation, and 30∘ external rotation, as well as pain at
the extremes of movement. Blood results showed raised inflammatory markers. White
blood cells, 11.7 × 109/L; C-reactive protein (CRP), 65 mg/L; and erythrocyte sedimentation rate (ESR), 51
mm/h. Radiographs of both hips were unremarkable. Magnetic resonance imaging (MRI)
was performed and showed increased signaling in the left piriformis muscle associated
with the presence of fluid collection ([Fig. 1]).
Fig. 1 Magnetic resonance imaging showing increased signaling in the left piriformis muscle
associated with the presence of fluid collection. (A) Sagittal plane weighted proton
density with fat suppression signal. (B) Coronal T1-weighted fat-suppressed signal
after gadolinium contrast. (C) Axial T1-weighted fat-suppressed signal after contrast
with gadolinium.
The patient was admitted for open surgical drainage of the piriformis muscle. The
results of the samples taken during the procedure showed a culture with the growth
of methicillin-resistant Staphylococcus aureus (MRSA) and histopathological examination with inflammatory infiltrate ([Fig. 2]). Antimicrobial susceptibility test showed vancomycin and trimethoprim-sulfamethoxazole
with minimum inhibitory concentrations (MIC) of ≤2 µg/mL and of ≤2/38 µg/mL, respectively.
The patient was treated with an intravenous antibiotic therapy (vancomycin 15 mg/kg
every 12 hours) during the first 10 days, followed by oral therapy (160 mg trimethoprim/800 mg
sulfamethoxazole every 12 hours) for up to 6 weeks. The patient made an uncomplicated
postoperative recovery and was discharged home on day 10. During a return visit 30
days after the surgery, the patient was asymptomatic. Six months after the surgery,
the patient did not present with pain or with any functional limitation.
Fig. 2 (A) Photomicrograph of piriformis pyomyositis. Fibromuscular tissue with a moderate
lymphohistiocytic inflammatory infiltrate (hematoxylin and eosin ×100). (B) Photomicrograph
of piriformis pyomyositis, higher magnification of inflammatory tissue (hematoxylin
and eosin ×400). (C) Photomicrographs of lymph node biopsy showing focal necrosis
surrounded by karyorrhectic debris, histiocytes and plasmacytoid lymphocytes (hematoxylin
and eosin, ×400).
Discussion
As far as we can determine, the present case report presents the first case reported
in the English language of piriformis muscle pyomyositis in a patient diagnosed with
KFD. The first detailed description of pyomyositis is attributed to Scriba in 1885.[1] It is more common in tropical countries, but its incidence has increased worldwide.
This increase seems to be related to an increase in individuals with compromised immune
systems (e.g., individuals with HIV, diabetes, organ transplantation, chemotherapy,
malignancies, rheumatic diseases). The exact incidence and prevalence rates are not
well-known.[2] The literature contains few reports of pyomyositis affecting the piriformis muscle.[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13] Unlike the present case, many of these reports discussed patients who had sciatica
with severe symptoms and sought medical care in the emergency room, experiencing large
changes in laboratory markers of infection ([Table 1]).
Table 1
|
Authors
|
Number of cases
|
Age (years)
|
Management
|
Outcome
|
|
Burkhart et al[3]
|
1
|
69
|
CT-guided aspiration
|
Full resolution of symptoms and return to sporting activities.
|
|
Chusid et al[4]
|
1
|
17
|
Intravenous antibiotics
|
By day 10 of treatment, the inflammatory markers of the patient returned to normal.
|
|
Wong et al[5]
|
3
|
45
|
Intravenous antibiotics
|
The pain gradually subsided and inflammatory markers returned to normal.
|
|
|
58
|
CT-guided aspiration
|
Fever and pain subsided after drainage and 2 weeks of intravenous antibiotics.
|
|
|
71
|
Intravenous antibiotics
|
The pain and fever subsided and the myositis resolved after 2 weeks of intravenous
antibiotics.
|
|
Wong et al[6]
|
1
|
31
|
Intravenous antibiotics
|
Blood parameters and clinical symptoms improved throughout the course of the treatment.
No residual symptoms.
|
|
Chong et al[7]
|
1
|
30
|
Intravenous antibiotics
|
A follow-up visit in the clinic showed full recovery with normalized ESR and CRP.
|
|
Toda et al[8]
|
1
|
06
|
Oral antibiotics
|
Final follow-up at 6 months revealed full range of motion of the hip joint with no
pain.
|
|
Koda et al[9]
|
1
|
42
|
Open surgical drainage followed by antibiotic treatment
|
Dramatic relief of pain after the surgery.
Patient returned to work after 2 months.
|
|
Giebaly et al[10]
|
1
|
18
|
Intravenous antibiotics
|
Full resolution of symptoms and return to sporting activities after 6 months.
|
|
Colmegna et al[11]
|
1
|
18
|
CT-guided aspiration
|
After 4 weeks, the patient was fully recovered.
|
|
Kinahan et al[12]
|
1
|
22
|
Intravenous antibiotics
|
Full recovery after 6 weeks of intravenous antibiotic therapy.
|
|
Gaughan et al[13]
|
1
|
34
|
Intravenous antibiotics
|
After 8 weeks, the patient was still using crutches to mobilize and was still reliant
on analgesics.
|
|
(current case)
|
1
|
23
|
Open surgical drainage followed by antibiotic treatment
|
Asymptomatic after 6 months.
|
In a study evaluating 676 cases of pyomyositis, the average age was 28.1 years; in
26.3% of the cases, the quadriceps represented the most commonly affected muscle group,
and involvement in more than one muscle group was found to occur in 16.6% of the cases.
In many instances, the infecting bacteria were not identified; however, among the
identified cases, S. aureus was responsible for 77% of the cases.[2] The pathogenesis of pyomyositis is still not completely understood. It is believed
that it occurs as a complication of transient bacteremia associated with a local muscle
tissue abnormality.[14] The evolution of pyomyositis can be clinically divided into three stages.[2]
[14] The invasive stage is subacute and occurs in between 1 and 3 weeks. The patient
presents with local pain, edema, fever, and leukocytosis. There is no pus. This stage
may regress or progress to the next stage. The suppurative stage is when the diagnosis
is usually made and is characterized by a worsening of symptoms, fever, and abscess
formation. However, because of its deep location, classic signs of inflammation may
be absent. If the suppurative stage remains undiagnosed and untreated, the infection
spreads, leading to the late stage, which is characterized by sepsis, septic shock,
and even death.[2]
[14]
Laboratory tests are able to detect variable leukocytosis, particularly in the invasive
stage, but the shift to the left occurs during the suppurative stage. The ESR and
CRP inflammatory markers are elevated but are not specific. Blood cultures are sterile
in between 70 and 80% of the cases.[14] Nuclear MRI is the most useful imaging methodology for the diagnosis of pyomyositis;
it reveals diffuse muscle inflammation and subsequent abscess formation. The administration
of a contrast helps in detecting an abscess. A muscle biopsy associated with tissue
culture remains the gold standard for the diagnosis.[14] In the present case, the patient was asymptomatic, without systemic effects of infection,
and with little change in laboratory tests, probably because of the use of trimethoprim/sulfamethoxazole
to prevent opportunistic infections during the treatment of lymphoma.
Pyomyositis is treated according to the stage in which it is diagnosed. During the
early stage, diffuse inflammatory disorders can be treated with antibiotics alone.[7] However, after the formation of an abscess, a drain should be performed, followed
by antibiotic therapy.[9] This treatment allows for a full recovery without sequelae in most cases. Drainage
can be accomplished via percutaneous puncture guided by ultrasound (US) or CT, and
open surgery is performed in cases of incomplete drainage, with extensive muscle damages
requiring extensive debridement. Intravenous antibiotic therapy should be applied
during the first 7 to 10 days, followed by oral therapy for up to 6 weeks.[2]
Our report presents an association between piriformis pyomyositis and the rare KFD.
Kikuchi–Fujimoto disease is a benign and usually self-limiting disease that mainly
affects women < 30 years old. Most cases are resolved within 6 months. Its etiology
is unknown, but a correlation with viral infections and autoimmune disorders has been
reported. The patient presents with fever, fatigue, swollen lymph nodes, and upper
respiratory tract symptoms. Often, the diagnosis is confused with other diseases such
as lymphoma, and it is confirmed using lymph node biopsy.[15]
Conclusion
Pyomyositis is a rare and potentially severe infection that can lead to septic shock.
The present case shows the need for a high level of suspicion in patients with compromised
immune systems so that treatment can be carried out at an early stage. The reviewed
medical literature shows that, despite the potentially severe infection occurs, the
treatment outcome is most commonly very good.
