A Rare Case of Concomitant Septic Arthritis, Osteomyelitis, and Pyomyositis Caused by Salmonella

A common causative organism in osteomyelitis in sickle cell disease is Salmonella. Septic arthritis and muscle infection due to Salmonella are much less common. We present a case of a 28-year-old woman with sickle cell disease who presented with left shoulder and elbow pain for two days. Physical examination revealed swelling of the left upper arm. The patient was initially treated for a sickle cell pain crisis. On hospital day 4, the patient developed a fever. She empirically started intravenous vancomycin and cefepime before her blood culture showed Salmonella. Subsequently, the antibiotic was changed to ceftriaxone. Synovial fluid analysis of the left shoulder revealed a white blood cell count of 53,250/mm3 with mostly neutrophils, and this led to a presumptive diagnosis of septic arthritis. She underwent a left shoulder arthroscopic irrigation and debridement. The synovial fluid culture was negative. Magnetic resonance imaging (MRI) revealed osteomyelitis in the left humerus, a 4.4 x 5 cm intramuscular abscess near the distal anterior humerus, and pyomyositis. Percutaneous abscess drainage was done. The patient was discharged home on ceftriaxone but returned 12 days later with worsening pain in her shoulder. Repeat MRI showed a complex glenohumeral joint effusion. She had an incision and drainage of her left shoulder. The patient was discharged on an eight-week course of ceftriaxone. Prompt diagnosis and early treatment are essential in reducing the mortality and morbidity associated with these joint, bone, and muscle infections.


Introduction
Patients with sickle cell disease who present with acute pain in long bones without fever may be suspected of having vaso-occlusive pain. However, they should also be evaluated for other causes of pain that require treatment other than opioids. Patients with sickle cell disease are at increased risk for orthopedic complications such as osteonecrosis and bone infarction, but also infections such as osteomyelitis and septic arthritis [1]. Another rare infection that has been reported in sickle cell disease is pyomyositis [2]. Pyomyositis is an infection of the muscle that initially presents with pain, swelling, and fever, and then tenderness and edema.
The most common cause of pyomyositis and septic arthritis in adults is Staphylococcus aureus. However, Salmonella is more common in sickle cell disease pediatric patients with osteomyelitis in the United States [3]. It is unusual to see nontyphoidal Salmonellae in joint, bone, and muscle infections since this bacterial organism is known to cause diarrheal illness. We present this case of an adult patient with sickle cell disease with Salmonella bacteremia complicated by the shoulder and elbow septic arthritis, humeral osteomyelitis, and pyomyositis.

Case Presentation
A 28-year-old woman with sickle cell disease presented to the emergency department with pain in her left shoulder and elbow for two days. There was no preceding trauma and no fever, cough, nausea, vomiting, or diarrhea. Oral ibuprofen and morphine provided minimal pain relief. The patient had been admitted 14 days prior because of a sickle cell crisis with pneumonia and a urinary tract infection. She lived with her family and was not an injection drug user. On physical examination, the temperature was 98.2°F, the blood pressure 132/92 mmHg, the pulse was 97 beats per minute, the respiratory rate was 17 breaths per minute, and the oxygen saturation was 100% while the patient was breathing ambient air. Her left upper arm was mildly swollen and tender. Passive and active range of motion of the left shoulder and elbow was limited. Radiography of the left shoulder showed no evidence of acute fracture, and radiography of the left elbow showed joint effusion ( Figure 1).

FIGURE 1: Radiography of the left elbow showing joint effusion (blue arrow)
Laboratory test results are shown in Table 1.

MRI: Magnetic Resonance Imaging
A repeat ultrasound of the left upper extremity showed a small fluid collection measuring 11.6 x 6.6 mm in the left lateral aspect of the arm. A left shoulder arthroscopic incision and drainage were performed. Aerobic, anaerobic, and mycobacterial cultures of the aspirated fluid showed no growth. She was discharged home on an eight-week course of ceftriaxone. She was clinically stable at her follow-up appointment nearly two months later.

Discussion
Musculoskeletal infection may not initially be suspected in a patient with sickle cell disease who presents with acute pain of an extremity. Differentiating between vaso-occlusive pain and joint, bone, and muscle infections tremendously affects management as antibiotics and surgical intervention may be required. Our patient presented with unilateral upper extremity pain without fever. Her restricted range of motion of shoulder and elbow joints implied that at least an oligoarthritis was involved. When she developed a fever, septic arthritis was immediately considered.
Salmonella is known to cause osteomyelitis in sickle cell disease patients. It has also been reported to cause pyomyositis and septic arthritis. Septic arthritis and pyomyositis can be seen in IV drug users but our patient did not have this risk factor. Her synovial fluid culture may have been negative for Salmonella because the synovial fluid was obtained after a week of antibiotic use. Her shoulder infection was severe since it required arthroscopy twice. The sensitivity of organism identification in synovial fluid may be lower than in blood.
In addition to surgery, our patient was administered ceftriaxone to treat septic arthritis, osteomyelitis, and pyomyositis. There are no randomized controlled trials on the efficacy of the optimum antibiotic treatment approach for osteomyelitis in patients with sickle cell disease [4]. No bone biopsy for an organism was pursued since the blood culture showed growth of Salmonella. The pyomyositis was detected on the MRI after the positive blood culture and arthrocentesis. If the pyomyositis was detected first, vancomycin would have been the empiric antibiotic of choice [5]. There was no need to monitor the creatine kinase since her myositis was infectious, not inflammatory.

Conclusions
This was an atypical clinical presentation of Salmonella infection as septic arthritis, osteomyelitis, and