Necrotizing Myositis: A Rare Necrotizing Soft Tissue Infection Involving Muscle

Introduction. Necrotizing myositis (NM) is an extremely rare necrotizing soft tissue infection involving muscle. Unlike similar infections (eg, necrotizing fasciitis, clostridial myonecrosis) that can be more readily diagnosed, NM can have a benign presentation then rapidly progress into a life-threatening condition with a mortality rate of 100% without surgical intervention. Case Report. A 74-year-old man with a history of prostate cancer with radiation therapy, seed implants, and 2 transurethral resection procedures presented to the emergency department after a fall. He was initially diagnosed and treated for urosepsis. Sixteen hours after presentation, he complained of pain and swelling of his right groin. Computed tomography of the abdomen and pelvis showed gas findings suspicious for necrotizing infection of the bilateral thighs. Surgical exploration revealed NM. Separate cultures from the left thigh and bladder grew Streptococcus intermedius, Clostridium clostridioforme, and Peptostreptococcus, suggesting a possible common source of infection from the prostate gland or the osteomyelitic pubic symphysis, which subsequently spread to the bilateral thighs. Conclusions. To the best of the authors’ knowledge, this is the first reported case of S intermedius and C clostridioforme causing NM. A high index of suspicion is required for extremely rare conditions like NM, because early diagnosis and surgical intervention significantly reduce mortality.

Necrotizing soft tissue infections (NSTIs) include a mild to aggressive spectrum of infections such as cellulitis, necrotizing fasciitis, and myositis involving dermis, subcutaneous tissue, fascia, and muscle.¹ Necrotizing fasciitis, a well-known NSTI, is a fascial infection which can progress to involve skin and muscle. In comparison, a lesser-known NSTI is necrotizing myositis (NM) that predominantly involves muscle and can later involve fascia and skin.² Necrotizing infections such as necrotizing fasciitis and clostridial myonecrosis are more readily diagnosed than NM, which requires a high index of suspicion. Necrotizing myositis is an extremely rare condition and also rarely reported. Prior literature has reported 30 cases over the last century,³ and a literature search for NM revealed about 80 cases from 1958 through 2017. This NSTI has a mortality rate approaching 100% without surgical intervention.¹

This report describes a case in which the patient presented with apparent urosepsis and was later found to have NM secondary to polymicrobial infection of Clostridium clostridioforme, Streptococcus intermedius, and Peptostreptococcus. To the best of the authors’ knowledge, this is the first case of NM caused by C clostridioforme and S intermedius.

A 74-year-old man presented to the NYU Winthrop Hospital’s emergency department (ED; Mineola, NY) complaining of lower extremity weakness and left inner thigh pain for the past 2 to 3 weeks, resulting from a fall when he got up to use the bathroom on the day of presentation. The patient denied any associated dizziness, palpitations, or loss of consciousness prior to the fall but reported new-onset right thigh pain since his arrival to the ED. The patient was seen 3 weeks prior in the ED with bilateral groin strain, and he was sent home after the initial workup was normal. He also was seen by his primary medical doctor, urgent care physician, and orthopedist over the last few weeks for extremity weakness and was scheduled for a magnetic resonance imaging (MRI) scan, but he fell prior to obtaining the study. Pertinent past medical history included hypertension, hyperlipidemia, benign prostatic hyperplasia, and prostate cancer treated with radiation and seed implant 10 years prior. His surgical history was significant for appendectomy, cholecystectomy, right inguinal hernia repair 6 years ago, and 2 transurethral resection procedures (TURPs), with the last TURP performed 16 months before this presentation.

In the ED, his vitals were significant for a blood pressure (BP) of 80/50 mm Hg and a temperature of 102°F. On physical examination, his bilateral lower extremities were noted to be edematous with a positive straight leg test on the right. No costovertebral angle tenderness was noted. Laboratory findings in the ED were significant for a white blood cell (WBC) count elevated to 30 000/mm³, hemoglobin (Hb) 7.9 g/dL, hematocrit (Hct) 24.5%, lactate 8.5 U/L, procalcitonin 20.7 mg/mL, prothrombin time 15 seconds, partial thromboplastin time 29.2 seconds, international normalizing ratio (INR) 1.38, blood urea nitrogen (BUN) 59 mg/dL, and creatinine (Cr) 1.5 mg/dL. A urine analysis was positive for occult blood 2+, leukocyte esterase 3+, WBC 97/mm³, red blood cell 139/mm³, and bacteria 4+. The patient received 3 L of intravenous normal saline in the ED; however, his BP did not respond appropriately. In light of the patient’s systemic inflammatory response syndrome, elevated lactate, and positive urine analysis, he was diagnosed with urosepsis, started on norepinephrine and meropenem (1 g intravenously every 8 hours) in addition to continued fluid resuscitation, and admitted to the medical intensive care unit for further management.

Sixteen hours after presentation to the ED, the patient began complaining of pain and swelling in his right groin. A bedside ultrasound was performed with findings suggestive of a hematoma. A subsequent computed tomography (CT) scan of the abdomen and pelvis without contrast (due to the elevation in BUN and Cr) was performed and revealed locules of gas and ill-defined low attenuation in the bilateral thigh musculature, highly suspicious for a gas-forming infection (Figure 1). Emphysematous cystitis, gas surrounding the prostate gland, and findings suspicious for pubic symphysis osteomyelitis also were noted.

The patient was then started on vancomycin (1 g intravenously every 12 hours) and clindamycin (900 mg in 5% dextrose in water every 8 hours) in addition to the meropenem dosage; a general surgery consult was placed, which deferred to wound care for further management.

On examination by the wound care team, the patient was noted to be awake, alert, and oriented with a BP of 94/48 mm Hg and temperature of 99.2°F. His bilateral medial thighs, suprapubic region, and scrotum were cellulitic with pain out of proportion to palpation on both thighs. No fluctuation or necrosis was appreciated and the abdominal examination was unremarkable. Laboratory findings included WBC 19 800 cells/mm³, Hb 6.8 g/dL, Hct 21%, BUN 60 mg/dL, blood Na 132 mEq/L, and albumin 2.1 gm/dL. One of 2 bottles for peripheral blood cultures were positive for Peptostreptococcus. At this time (28 hours after admission), there was a high suspicion for necrotizing infection and the patient was taken to the operating room for debridement (35 hours after admission) on the same day.

The patient was placed in the lithotomy position and bilateral medial thigh fasciotomies were performed (Figure 2). A copious amount of malodourous pus and multiple areas of necrotic muscle were encountered. A separate transverse pubic incision revealed no evidence of pus or necrotic muscle (Figure 3). The incisions were packed open to allow continued drainage, and daily debridements were performed on the following 3 postoperative days (PODs) until the wound was clear of necrotic tissue. Pathological analysis of tissue specimens collected from the thighs revealed fragments of partially necrotic skeletal muscle associated with purulent exudate (Figure 4). Cultures obtained separately from the left thigh and bladder revealed similar pathogens (S intermedius and C clostridioforme), indicating a possible common source of infection from the prostate cancer or spread of infection from osteomyelitis of the pubic symphysis, with subsequent spread to the bilateral thighs through the pubic symphysis.

A peripherally inserted central catheter (PICC) was placed and antibiotics were adjusted per recommendations from Infectious Disease. Daily dressing changes were performed for each wound with quarter-strength sodium hypochlorite for the suprapubic wound and until placement of negative pressure wound therapy (NPWT) for the bilateral thighs. A repeat CT on POD 4 showed post debridement changes and gas in pubic symphysis (Figure 5). Negative pressure wound therapy (V.A.C. VERAFLO; Acelity, San Antonio, TX) was applied to each thigh on POD 6 with a pressure of -125 mm Hg and intermittent irrigation of betaine-polyhexanide every 3 hours. Concomitant treatment with hyperbaric oxygen therapy (HBOT) was initiated on POD 7, and the patient received 1 session of HBOT at 2.5 ATA for 90 minutes daily, with a total of 8 sessions over the course of his hospital stay.

On POD 9, purulent drainage was noted from the right thigh wound during NPWT dressing change and the patient was taken to the operating room for an additional washout and debridement. Negative pressure was discontinued on the right thigh and a quarter-strength sodium hypochlorite dressing was used until discharge. The NPWT was continued for the left thigh. A cystogram performed on POD 10 showed extravasation of contrast from the inferior aspect of the bladder to the pubic symphysis and right medial thigh (Figure 6) and a suprapubic catheter was placed. The cystogram also revealed findings consistent with pubic symphysis osteomyelitis (Figure 6A). The remainder of the hospital stay was unremarkable, and the patient was discharged on POD 14 with outpatient follow-up in the wound clinic.

Upon discharge, wound care was performed with gauze soaked in quarter-strength sodium hypochlorite for all 3 wounds, and NPWT with -125 mm Hg was ordered for placement on the bilateral thighs in the rehabilitation facility. In addition, NPWT silver sponges (Acelity) were used specifically for the right thigh wound and a combination silver/black sponge (Acelity) was used for the left thigh wound.

Following discharge, the patient was seen regularly in the wound care clinic and NPWT was used for 27 days post discharge. He also received an additional 22 sessions of HBOT as an outpatient for a total of 30 sessions. Over the next 2 months, the left thigh wound became significantly smaller and the right thigh and suprapubic wounds healed completely.

Necrotizing soft tissue infections are an aggressive group of infections requiring immediate surgical attention. Although NSTIs are known for their fulminant disease course, patients can present with vague, nonspecific symptoms before rapidly progressing to life-threatening septic infection, thereby requiring a high index of suspicion. Necrotizing myositis is a rarely encountered NSTI involving the skeletal muscle. Various pathogens have been identified in NM cases and the organisms commonly isolated are group A beta-hemolytic Streptococcus (GABHS), C perfringens, and C septicum. To the best of the authors’ knowledge, this report is the first case of NM caused by C clostridioforme and S intermedius.

Patients with a NSTI may have nonspecific clinical findings with or without pain, swelling, and redness of the affected area. Worsening pain out of proportion to physical exam, edema, and inability to bear weight may occur as the disease progresses. Initially, the skin overlying the affected area may appear normal but become discolored with bullae, blisters, vesicles, or petechiae as the infection progresses. Systemic findings such as fever, tachycardia, hypotension, and shock may be present. Although NSTI is a clinical diagnosis, the aforementioned signs and symptoms occur in only 10% to 40% of patients.¹ Laboratory findings are nonspecific and often show elevated WBC, Cr, lactate, Cr kinase, and coagulopathy.¹ 

Sensitivities of CT and MRI in detecting NSTI are 80% to 85% and 90% to 100%, respectively.² Although MRI is a more sensitive imaging modality, it could potentially delay treatment, making CT a diagnostically convenient early imaging option.² Computed tomography can demonstrate air within the fascia, thickening and edema of the involved muscle/fascia, fluid tracking, lymphadenopathy, and deep tissue collections,² whereas MRI can demonstrate subcutaneous thickening with fluid collection and inflammatory response to the muscle.³ As NSTIs are clinically diagnosed, imaging results should not delay surgery in the presence of strong clinical suspicion.²

Management of NSTIs include prompt diagnosis and early surgical intervention. Surgery within 24 hours significantly increases survival.⁴ Surgical-site inspection within 24 hours following initial debridement, serial debridement every 48 to 72 hours, and removal of necrotic tissue are important management steps.⁴ Although the benefit of adjunctive HBOT remains controversial, the results of recent, small, retrospective studies have supported the use of HBOT for patients with NSTIs.^5,6

Histopathology of tissue obtained during surgery is important to confirm the diagnosis and differentiate a NSTI from idiopathic inflammatory myopathy (eg, polymyositis, dermatomyositis, inclusion body myositis). Histologically, NM demonstrates interstitial inflammation with muscle fiber necrosis⁷ and lacks the mononuclear inflammatory cell infiltrates seen in idiopathic inflammatory myopathy (Figure 4A). Tissue and culture specimens obtained during surgery also are important for organism identification and subsequent, targeted antibiotic treatment. Organisms identified in this case report were S intermedius, C clostridioforme, and Peptostreptococcus. Macnicol⁸ described a case of myositis caused by S milleri in 1977, but the exact species involved was not reported. S intermedius, a normal flora of oral cavity and gastrointestinal tract, can cause systemic infections and abscesses⁹ and, when isolated, is considered a true pathogen.¹⁰ It has many virulent strains, of which strain B-196 is associated with pyomyositis, osteomyelitis, sepsis, arthritis, and bronchopulmonary infections.^11,12 Osteomyelitic changes seen on the present patient’s CT and cystogram can be attributed to the purulent infection eroding the adjacent bone and also the osteomyelitic properties of virulent B-196 strain of S intermedius. S intermedius is known to produce a cytolytic toxin called intermedilysin, an important virulent factor for deep abscess.¹³ Hyaluronidase and deoxyribonuclease are other potent enzymes produced by S intermedius that aid in spreading infections through tissues by causing liquefaction and pus formation.¹⁴

C clostridioforme is an anaerobic, gram-positive bacillus that stains gram negative. It is part of normal colonic microflora.¹⁵ It is known to cause severe bacteremia, necrotizing fasciitis, pelvic-intraabdominal abscesses, and postoperative wound infections, especially in abdominal, perineal, and perianal regions.¹⁶ As in the present patient, cancer was an underlying condition in previously reported cases.¹⁶ 

Peptostreptococcus is an anaerobic, gram-positive bacterium found in the normal flora of mucocutaneous surfaces. It is commonly isolated from infections such as deep-organ abscesses. Three cases of Peptostreptococcus were reported as a cause of NM in the year 1972.¹⁷ Research has demonstrated the concept of microbial synergy (ie, promoting and enhancing the growth of other organisms) as an important contributing virulence factor for developing deep infections, thereby indicating that the presence of Peptostreptococcus along with other virulent organisms (S intermedius and C clostridioforme as in this case) has the potential to accelerate sepsis and increase mortality.¹⁸

Necrotizing soft tissue infections, particularly NM, are associated with high morbidity and mortality rates; therefore, a high index of suspicion is required for early diagnosis. The most common causative organisms are GABHS and C perfringens; however, rare organisms like S intermedius, C clostridioforme, and Peptostreptococcus also can lead to aggressive NM. Patients presenting with NM can be managed by a dedicated wound care team. Treatment includes prompt surgical intervention and broad-spectrum antibiotics. Surgical intervention within 24 hours significantly increases survival, emphasizing the importance of rapid diagnosis and expeditious treatment.

Authors: Harika Boinpally, MD¹; Raelina S. Howell, MD¹; Bebu Ram, MD²; Virginia Donovan, MD²; Michael Castellano, MD¹; Jon S. Woods, MD¹; and Scott Gorenstein, MD, FACEP¹

Note: We would like to thank the NYU Winthrop Department of Surgery (Mineola, NY) and the NYU Winthrop Wound Healing team for their support.

Affiliations: ¹Department of Surgery, NYU Winthrop Hospital, Mineola, NY; and ²Department of Pathology, NYU Winthrop Hospital

Correspondence: Scott Gorenstein, MD, FACEP, Clinical Director, Division of Regenerative Medicine, Department of Surgery, NYU Winthrop Hospital, 259 1st Street, Mineola, NY, 11501; sgorenstein@nyuwinthrop.org

Disclosure: The authors disclose no financial or other conflicts of interest.