During the first hospitalization, the hemoglobin level was 13.7 g/dL; platelets, 264,000/μL; and white blood cell count, 11,200/μL, with 72.6% neutrophils and 15.5% lymphocytes. Human immunodeficiency virus 1 and 2 antibodies were negative. Erythrocyte sedimentation rate was 70, and antinuclear antibody screening was positive with an atypical specked Anti-Ro/SSA pattern and a titer of 80. Perinuclear antineutrophil cytoplasmic antibodies and antineutrophil cytoplasmic antibodies with cytoplasmic staining pattern were not detected.
For the second hospitalization, the hemoglobin level was 10.9 g/dL; platelets, 128,000/μL; and white blood cell count, 2800/μL, with 73.7% neutrophils and 18.3% lymphocytes. Toxoplasma and cytomegalovirus serologies (immunoglobulin [Ig] M and IgG) were negative. Human immunodeficiency virus RNA was not detected. Parvovirus IgM was negative, with IgG antibody detected.
Pulse-field gel electrophoresis was performed using Sma I restriction endonuclease and interpreted using standard guidelines. A sample of USA 100, 300, 400, and 800 was compared with our patient's isolate using pulse-field gel electrophoresis. The SCC mec element type and the polymerase chain reaction amplification of the genes encoding Panton-Valentine Leukocidin (PVL) luks-pv and lukf-pv were performed using techniques described elsewhere.6
Staphylococcal chromosomal cassette mec IV was identified in the patient's CA-MRSA. Pulse-field gel electrophoresis demonstrated a band pattern identical to USA 300, and the assay for PVL genes was positive.
Pyomyositis is a suppurative infection of striated muscle characterized by localized muscle pain, swelling, and tenderness.7 It is hypothesized that pyomyositis initially originates from a transient bacteremia that would not cause clinically evident infection in most individuals. Muscle trauma is thought to be the inciting event leading to seeding of bacteria into the traumatized muscle. Intravenous drug users and immunocompromised patients have been more susceptible to seeding at skeletal muscle sites. Few cases have been described in previously healthy individuals such as our case. Pyomyositis is characterized by 3 distinct stages. These stages are more apparent in untreated patients where the disease may progress to septicemia and death. The mortality rate in tropical regions has been reported as high as 14%.8
During stage 1, patients experience cramps, localized edema, and pain in the infected muscle. Mild leukocytosis and low-grade fever along with a woody texture on palpation are usually present. Aspiration at this stage usually yields little or no discharge.
Stage 2 follows, leading to a frank suppurative stage with abscess formation that occurs 10 to 21 days after symptom onset. Aspiration yields purulent discharge, and up to 90% of patients present in this stage.6 The muscle becomes fluctuant, sometimes warm with little to no skin manifestations over the site of infection. The patient has more severe fever, leukocytosis, and generalized constitutional symptoms of infection.
The septicemic stage of the disease, stage 3, is when dissemination into the bloodstream occurs. Septic emboli along with the formation of multiple abscesses may occur at distant sights. This is the stage we observed in our case.
Cases of CA-MRSA may occur in patients without underlying risk factors, such as intravenous drug use and recent antimicrobial therapy, or associated with a health care facility. Our patient had no exposure to a health care facility and had no known previous infection with S. aureus. Pulse-field gel electrophoresis performed on the chest wall aspirate revealed a band pattern identical to the USA 300 strain of bacteria, and it was SCC mec type IV and PVL (+).
Kikuchi-Fujimoto disease is a rare hyperimmune response to infection, malignancy, or less commonly, drugs.9 The disease usually occurs in the third or fourth decade of life and has a 4:1 female-to-male predominance.10 Kikuchi-Fujimoto disease usually follows a benign self-limited course, but in some cases, it may take many months to resolve.10 There are no previous reports of transient pancytopenia with KFD. Because pancytopenia resolved spontaneously with improvement of KFD in the case above, a possible causal association is surmised.
Consideration of CA-MRSA has become increasingly important when initiating empirical antimicrobial therapy for soft tissue infections in immunocompetent patients and justifies an appropriate diagnostic approach with imaging studies if pyomyositis is suspected.11 Our patient extends the spectrum of clinical manifestations caused by CA-MRSA USA-300 genotype. Prompt diagnosis and therapy with appropriate antibiotics was associated with a successful outcome. Although pyomyositis has been a rare occurrence, to date, KFD has not been reported in association with CA-MRSA.
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11. Kong NCT, Asmah J, Lim VKE, et al. Pyomyositis revisited. Ann Acad Med Singapore