Holly Kirkland-Kyhn, PhD, FNP, GNP, CWCN, FAANP; Melania Howell, BSN, BS, RN, CWOCN, DAPWCA, DNPc; and Salomé Loera, BSN, RN, PCCN, CCRN-CMC, DNPc
Pyomyositis is a rare bacterial infection of skeletal muscles classified as primary or secondary.1 A key differentiation between the forms is the location of the patient at the time of disease development. Patients in the tropical regions of Africa and the South Pacific exhibit the primary form of the disease.1 In these settings, the patients are relatively young, often ranging from 2 to 5 years old.1 Pyomyositis occurring in the world’s temperate regions (eg, North America) is classified as secondary, and patients are usually older.1 The increasing incidence of pyomyositis in temperate areas is mostly associated with an underlying disease process compromising the immune system.1 Clinicians observe secondary pyomyositis in patients with immunodeficiency, trauma, intravenous drug use, concurrent infection, diabetes, and malnutrition.2 Blunt force trauma or vigorous exercise account for 20% to 50% of pyomyositis cases.2 Additionally, spontaneous hematoma formation from anticoagulants for deep vein thrombosis prophylaxis may also cause the infection.2 Males appear to be affected more often than females at a 3:1 ratio.3
The exact pathophysiology of pyomyositis is unknown. Researchers theorize that the condition results from the hematogenous spread of infection through the bloodstream.3,4 The disease behaves like a malignant metastasis in which the bacteria travel through the bloodstream and seed in the larger striated muscle groups of the lower body.3 There are 3 distinct phases of pyomyositis. During the initial invasive stage, pyomyositis signs and symptoms are vague and nonspecific.1 Patients may exhibit fever, pain, leukocytosis, and a woody edema.2,3 Interestingly, due to the deep-seated location of the infection, fluctuance and erythema are absent.2,5 In the second stage, 10 to 21 days after the original insult, muscle pain increases, edema worsens, and fever persists.3 As the infection progresses to the suppurative third stage, the patient exhibits signs and symptoms of systemic inflammatory response syndrome.3 The condition becomes disseminated, resulting in septicemia, septic shock, and multisystem organ failure.2,3
Globally, Staphylococcus aureus is the most common culprit of the disorder, although clinicians are increasingly reporting methicillin-resistant S aureus.2 The most common organisms obtained via wound cultures during surgery are S aureus, β-hemolytic Streptococcus, and the gram-negative bacilli Escherichia coli.2
Assessment. Clinicians can differentiate pyomyositis from pressure ulcers/injuries (PU/Is) and necrotizing soft tissue injury (NSTI) or necrotizing fasciitis by starting with a detailed patient history.3 Practitioners should be attuned to reports of recent or remote blunt force trauma to the area of concern.2,3
Patients with PU/Is exhibit tissue damage over vulnerable, high-risk, bony prominences or under medical devices.6,7 PU/I infection with associated bacteremia is rare.6 A PU/I infection is diagnosed by examining the wound bed for necrosis, large amounts of exudate level, malodor, periwound cellulitis, fluctuance, or induration.6 Also, patients with an infected PU/I may not exhibit sepsis, unlike the patient with pyomyositis.3,7 Infected PU/Is are usually full-thickness ulcerations, unlike pyomyositis, which has vague initial presenting symptoms.3,7
Clinicians may confuse pyomyositis with an NSTI. Necrotizing fasciitis evolves rapidly and involves the superficial and deep fascia.3 Pyomyositis, however, affects large striated skeletal muscle groups.3 NSTIs are more apparent as the patient presents with hyperemia, blisters, and subcutaneous emphysema.3 Imaging can help to distinguish pyomyositis from NSTIs.3
Diagnosis. Magnetic resonance imaging is the best diagnostic tool to identify pyomyositis.1–3 Practitioners may also use computed tomography or ultrasound.2,3 The patient with pyomyositis exhibits abnormal laboratory values, including leukocytosis, positive blood, or deep wound cultures.1,3 Latter stages of pyomyositis present with signs of sepsis.1,3 Immunocompromised patients may have polymicrobial pyomyositis infection.1,3
Case study. A 62-year-old man jumped out of the second story of his burning apartment building. He sustained burns on his bilateral buttocks and upper extremities involving 24% body surface area. Medical history included chronic and recurrent nephrolithiasis with hydronephrosis, skin cancer with recent radiation therapy, and type 2 diabetes. He underwent debridement and grafting of his burns 24 hours after admission and was given anabolic steroids to support muscle development. He was fully mobile but reluctant to engage in physical therapy and occupational therapy daily.
Approximately 2 weeks into the hospital stay, an abscess was found on the left medial buttock and the patient had a concurrent fever of 102°F (Figure 8). This left buttock abscess was treated with incision, drainage, and local wound care. He then underwent a uroscopy and received intravenous antimicrobial therapy for the treatment of a urinary tract infection. The following week he complained of buttock pain and a fever developed. Computed tomography and nuclear scans were performed due to persistent leukocytosis with fever. Imaging results revealed a loculated fluid collection in the right gluteal muscle, leading to diagnosis of pyomyositis. The progression of the abscess from the left gluteal area to the right corresponded with the diagnosis of pyomyositis, as opposed to a PU/I. Moreover, most often PU/Is occur over the bony prominences and not between the gluteal cleft. Initial management included needle-guided aspiration of the abscessed area. Surgical intervention was necessary due to septic shock. Intraoperative findings included gluteal muscle ischemia and abscess. Presumably, the right gluteal infection continued to progress under pressure, causing necrosis, which was relieved with surgical debridement. Multiple surgeries were required to excise the nonviable gluteal musculature.
1. Comegna L, Guidone PI, Prezioso G, et al. Pyomyositis is not only a tropical pathology: a case series. J Med Case Rep. 2016;10(1):372. doi:10.1186/s13256-016-1158-2
2. Lemonick DM. Non-tropical pyomyositis caused by methicillin-resistant Staphylococcus aureus: an unusual cause of bilateral leg pain. J Emerg Med. 2012;42(3):e55–e62. doi:10.1016/j.jemermed.2008.12.020
3. Al-Dossari R, Zekri S. Failed early intervention of pyomyositis in an immunocompetent individual. Case Rep Infect Dis. 2018:4296976. doi:10.1155/2018/4296976
4. Panikkath D, Tantrachoti P, Panikkath R, Nugent K. Streptococcus agalactiae pyomyositis in diabetes mellitus. Proc (Baylor Univ Med Center). 2016;29(3):290–291. doi:10.1080/08998280.2016.11929439
5. Agarwal N, Aroor S, Saini P, Gupta A, Kaur N. Pyomyositis: are we missing the diagnosis? Surg Infect (Larchmt). 2016;17(5):615–621. doi:10.1089/sur.2015.191
6. Baranoski S, Ayello EA. Wound Care Essentials: Practice Principles. 4th ed. Wolters Kluwer; 2015.
7. Espejo E, Andrés M, Borrallo R-M, et al. Bacteremia associated with pressure ulcers: a prospective cohort study. Eur J Clin Microbiol Infect Dis. 2018;37(5):969–975. doi:10.1007/s10096-018-3216-8