A case of Pyomyositis by Sarah Kerr

1. Noon Conference
Sarah Kerr, MS3

2. Summary Statement
Patient is a 59-year-old man with ALL who
presented for cycle 2B of hyper-CVAD
chemotherapy but on further evaluation was
found to have leukocytosis, as well as
worsening R elbow and R thigh erythema,
edema and pain.
DDx?

3. Imaging
• MRI Upper Extremity:
Myositis; no evidence of abscess, osteomyelitis
or septic arthritis.
• MRI Lower Extremity:
Focal intramuscular abscess in the biceps
femoris muscle with mild necrosis of the
surrounding tissue.

4. Pyomyositis
• A purulent infection of skeletal muscle that
arises from hematogenous spread of bacteria
– usually with abscess formation.
• Predisposing factors: immunodeficiency,
trauma, injection drug use, concurrent
infection.

5. Pyomyositis
• Most common pathogen = staph aureus
(MRSA in up to 25% of these cases).
• E. Coli pyomyositis emerging infection in those
with hematologic malignancy.

6. Clinical Presentation
FEVER, LOCALIZED CRAMPY MUSCLE PAIN, SWELLING
• 3 clinical stages
• Greater than 90% of patients present with stage 2:
occurs 10-21 days after onset of symptoms and can
be characterized by fever, exquisite muscle
tenderness, edema, marked leukocytosis. Frank
abscess MAY be clinically apparent. Aspiration yields
pus.

7. Diagnosis
• MRI
• Fluid cultures

8. Treatment
• Patients who present with stage 2 or 3 usually
require drainage in addition to antibiotic
therapy.
• Immunocompetent: vancomycin.
• Immunocompromised: vancomycin + broad-
spectrum coverage for gram neg. and
anaerobes.

9. Pyomyositis Polymyositis
Pathophysiology Hematogenous spread of
bacteria in
immunocompromised
patient
Autoimmune
Clinical
Presentation
Fever, swelling, crampy
localized muscle pain
Symmetric proximal muscle
weakness
Diagnostics MRI, Fluid aspirate Muscle enzymes,
+ANA/anti-jo-1, muscle
biopsy
Treatment Broad-spectrum antibiotics Corticosteroids,
methotrexate