A 39-year-old man with a past medical history of HIV and bipolar disorder presented to the emergency department with a complaint of right hip pain for six days. He noted that he was riding the bus when he suddenly experienced a sharp pain that went from his right hip to his right knee. He went to an outside hospital and was diagnosed with a hip sprain.
The patient reported that his thigh was swollen and that he was unable to walk because of the pain. He denied any rashes, and noted that his last CD4 count was “high.” He had been off his medications for a month. He also noted body aches, and was very uncomfortable while giving his history.
A chart review revealed that his last CD4 count was in the 300s. His temperature was 38.3°C and heart rate was 105 bpm at that outside hospital. At our hospital, his oxygen saturation was 99% on room air, heart rate was 93 bpm, blood pressure was 108/57 mm Hg, temperature was 35.8°C. He was oriented to person, place, and time, but was diaphoretic, appeared distressed, and was trying to lean onto his left side. He was acutely tender right below his hip on the right and jumped off the bed on palpation of his lateral and anterior thigh. His right thigh was more swollen than the left. He didn't have any calf pain, but did have 2+ dorsalis pedis pulses. His skin was all the same temperature; there was no redness or warm on his left and right thigh. He had no skin changes on his legs at all.
His laboratory tests came back as white blood cell count: 60.3; erythrocyte sedimentation rate: 130 mm/hr; C-reactive protein: 364.6 mg/L; sodium: 126 mmol/L; creatinine: 1.47 mg/dl (normal range 0.70-1.30 mg/dL); and lactate whole blood venous: 4.6 mmol/L. What does this patient have? What treatment should he get?
Find the diagnosis and case discussion on the next page.
Diagnosis: Infectious Myositis or Pyomyositis
Infectious myositis, or pyomyositis, is a bacterial infection of the skeletal muscle. It was first called “tropical myositis” in 1885. (Dtsch Z Chir 1885;22:497.) The term “temperate pyomyositis” was introduced in 1971. (N Engl J Med 1971;284:196.) Seventy-five percent of the cases seen in temperate climates are caused by Staphylococcus aureus, but Group A Streptococcus, E. coli, Klebsiella, Pneumococcus, Neisseria, Haemophilus, and Pseudomonas, to name a few, also cause this infection. (Clin Infect Dis 1992;15:668.)
Pyomyositis usually affects the larger muscle groups in the body such as the iliopsoas, quadriceps, glutei, biceps, and abdominal muscles. (Infect Dis Clin Prac 1998;7:265.) Trauma might set up the muscle for this infection in otherwise healthy patients. (J Bone Joint Surg Am 1990;72:1240.) Patients who use IV drugs (Emerg Med J 2003;20:299) and are immunocompromised are at higher risk as well. (J Bone Joint Surg Am 1993;75:588.)
The progression of pyomyositis falls in three stages. (Am J Surg 1979;137:255.) The invasive stage has inflammation and swelling to the muscle along with a low-grade fever and pain. The painful area can have a “wooden consistency,” and often doesn't have any erythema. A needle aspiration might not yield any pus. The diagnosis is often missed at this stage because of the nonspecific signs and symptoms. (J Bone Joint Surg Am 1990;72:1240.) The suppurative stage is when abscesses develop. The muscle might appear tense, but you might not see any other skin changes to clue you in to a deeper infection and abscess. Needle aspiration would be helpful at this stage and would yield a return of pus. The late stage occurs if no treatment has been initiated; the patient will get systemically ill. (Postgrad Med J 2004;80:267.)
Ultrasound can be helpful in the diagnosis. Computed tomography and magnetic resonance imaging are the better imaging techniques. (Radiology 1995;197:279.) That being said, CT has missed cases that MRI has picked up, so MRI is probably the best imaging choice in patients for whom you have high suspicion for pyomyositis even if the CT scan comes back normal. (Skeletal Radiol 1988;17:190.)
The treatment of pyomyositis usually includes broad-spectrum antibiotics, especially in immunocompromised patients, as well as incision and drainage and surgical debridement.
This can be a difficult diagnosis to make. Cases can present with initially vague symptoms and no systemic signs of developing infection. Clinicians also need to consider cellulitis, osteomyelitis, septic arthritis, contusion, necrotizing fasciitis, traumatic hematoma, and even deep venous thrombosis. It is important at least to consider pyomyositis if a patient presents with fever, an elevated white blood cell count, muscle pain, and immunocompromise.
This patient went from the ED to the OR, where a large amount of pus was drained from his right thigh. He was started on broad-spectrum antibiotics, and is doing well after two more returns to the OR.
Share this article on Twitter and Facebook.
Access the links in EMN by reading this on our website or in our free iPad app, both available at www.EM-News.com.
Comments? Write to us at firstname.lastname@example.org.