BACKGROUND: Necrotizing myopathies and muscle necrosis can be caused by immune-mediated mechanisms, drugs, ischemia, and infections, and differential diagnosis may be challenging.
METHODS: We describe a case of diabetic myonecrosis complicated by pyomyositis and abscess caused by Escherichia coli. A white woman in her late forties was admitted to the hospital with a 1.5 week history of bilateral swelling, weakness, and mild pain of the lower extremities and inability to walk. She had a history of type 1 diabetes complicated by diabetic retinopathy, neuropathy, nephropathy, and end-stage renal disease. C-reactive protein was 203 mg/l, while creatinine kinase was only mildly elevated to 700 IU/l. Magnetic resonance imaging of her lower limb muscles showed extensive edema, and muscle biopsy was suggestive of necrotizing myopathy with mild inflammation. No myositis-associated or myositis-specific antibodies were detected. Initially, she was suspected to have seronegative immune-mediated necrotizing myopathy, but later her condition was considered to be explained better by diabetic myonecrosis with multifocal involvement. Her symptoms alleviated without any immunosuppressive treatment. After a month, she developed new-onset and more severe symptoms in her right posterior thigh. She was diagnosed with emphysematous urinary tract infection and emphysematous myositis and abscess of the right hamstring muscle. Bacterial cultures of drained pus from abscess and urine were positive for Escherichia coli. In addition to abscess drainage, she received two 3-4-week courses of intravenous antibiotics. In the discussion, we compare the symptoms and findings typically found in pyomyositis, immune-mediated necrotizing myopathy, and diabetic myonecrosis (spontaneous ischemic necrosis of skeletal muscle among people with diabetes). All of these diseases may cause muscle weakness and pain, muscle edema in imaging, and muscle necrosis. However, many differences exist in their clinical presentation, imaging, histology, and extramuscular symptoms, which can be useful in determining diagnosis. As pyomyositis often occurs in muscles with pre-existing pathologies, the ischemic muscle has likely served as a favorable breeding ground for the E. coli in our case.
CONCLUSIONS: Identifying the etiology of necrotizing myopathy is a diagnostic challenge and often requires a multidisciplinary assessment of internists, pathologists, and radiologists. Moreover, the presence of two rare conditions concomitantly is possible in cases with atypical features.

Nocardia pyomyositis in immunocompetent patients is a rare occurrence. The diagnosis may be missed or delayed with the risk of progressive infection and suboptimal or inappropriate treatment. We present the case of a 48-year-old immunocompetent firefighter diagnosed with pyomyositis caused by Nocardia brasiliensis acquired by direct skin inoculation from gardening activity. The patient developed a painful swelling on his right forearm that rapidly progressed proximally and deeper into the underlying muscle layer. Ultrasound imaging of his right forearm showed a 7-mm subcutaneous fluid collection with surrounding edema. Microbiologic analysis of the draining pus was confirmed to be N brasiliensis by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) Mass Spectrometry. After incision and drainage deep to the muscle layer to evacuate the abscess and a few ineffective antibiotic options, the patient was treated with intravenous ceftriaxone and oral linezolid for 6 weeks. He was then de-escalated to oral moxifloxacin for an additional 4 months to complete a total antibiotic treatment duration of 6 months. The wound healed satisfactorily and was completely closed by the fourth month of antibiotic therapy. Six months after discontinuation of antibiotics, the patient continued to do well with complete resolution of the infection. In this article, we discussed the risk factors for Nocardia in immunocompetent settings, the occupational risks for Nocardia in our index patient, and the challenges encountered with diagnosis and treatment. Nocardia should be included in the differential diagnosis of cutaneous infections, particularly if there is no improvement of \"cellulitis\" with traditional antimicrobial regimens and the infection extends into the deeper muscle tissues.

Pyomyositis is a purulent infection of skeletal muscle that is mostly observed in tropical countries. Aseptic pyomyositis is a rare, potentially life-threatening disorder characterized by the formation of sterile pus in muscle. We present a case of 53-years old female, diagnosed case of seropositive rheumatoid arthritis, presented with pain and swelling of the right calf muscle for 2 weeks. There was no history of fever, cough, skin erythema, no history of prolonged standing or immobility, or fetal loss. The diagnosis was made as rheumatoid arthritis with autoimmune pyomyositis, and the patient was treated with oral prednisolone 1mg/kg body weight in tapering dose, cs DMARDS, (methotrexate 25 mg once a week, and leflunomide 20mg daily hydroxychloroquine 200 mg daily orally) and another supportive treatment along with surgical drainage of pus was done. There was complete resolution of the initial lesion and remission of the primary disease in 3 months.

UNASSIGNED: An intramuscular abscess of the subscapularis is a rare phenomenon but important pathology for surgeons to be aware of because clinical deterioration can be rapid and diagnosis difficult. The presentation often mimics other common shoulder pathologies with subacute shoulder pain and stiffness. Early diagnosis, antibiotics and surgical drainage are critical to reduce the spread and joint destruction.
UNASSIGNED: A search of PubMed and Google Scholar databases identified cases of subscapular intramuscular abscess. Data collected about each case included patient demographics, presentation, pathology, surgical treatment and outcome. The authors report one additional subscapular abscess case.
UNASSIGNED: Data from 17 cases of subscapular abscess were found, 16 in the literature and one case described by the authors. Sixteen of 17 cases (94.1%) presented with shoulder pain and reduced range of motion worsening over a mean of 6.7 days prior to presentation. Surgical approaches utilised included a posterior inferomedial approach, deltoid-pectoral approach and one posterior inferolateral approach.
UNASSIGNED: From the limited data available regarding subscapular intramuscular abscess, the authors make the following recommendations: (1) Empirical antibiotics covering Staphylococcus aureus +/- methicillin-resistant Staphylococcus aureus, (2) drainage is indicated in all cases; and (3) tendon-sparing approaches can access an abscess in most locations within the subscapular space.

Muscular tuberculosis as a primary focal lesion in an immunocompetent individual without any underlying bone involvement is a rare finding. The authors present a case of a young female in her 30s who presented with complaints of recurrent discharging sinus in the posteromedial aspect of the proximal right thigh for eight months. The patient was treated by surgical debridement followed by antitubercular therapy (ATT) and has shown full recovery during the post-eight-month treatment period. Such a presentation of primary tubercular pyomyositis imposes a diagnostic as well as a therapeutic challenge.

Primary tropical pyomyositis, commonly caused by Staphylococcus aureus, is characterised by suppuration in skeletal muscles, which manifests as single or multiple abscesses. Another rare causative organism is Mycobacterium tuberculosis in endemic areas. Here, we report a case of primary tuberculous pyomyositis presenting as septic arthritis of the right knee and multiple site pyomyositis of the right thigh and chest wall. A tuberculous aetiology was overlooked at first, which resulted in a diagnostic delay. The patient was initially diagnosed, using ultrasonography, MRI and an absence of systemic symptoms of tuberculosis, with bacterial pyomyositis and treated with broad-spectrum antibiotics. However, further investigations performed on knee joint aspirate yielded negative cultures and a positive cartridge-based nucleic acid amplification test, which, along with a non-resolution of his symptoms, suggested a primary tuberculous pyomyositis. He was successfully managed with incision and drainage of the lesions and completion of anti-tubercular therapy.

Pyomyositis is an uncommon primary infection of skeletal muscle resulting in muscle inflammation followed by pus formation. Pyomyositis is typically caused by Staphylococcus aureus (S. aureus), and most cases are associated with skin penetration and/or immunosuppressive conditions in tropical or even temperate climates. We report a previously healthy, immunocompetent 44-year-old man who presented with fever and right lower back pain. He had received an analgesic injection for his back pain 12 days prior to this visit. His clinical course was further complicated by the coexistence of multiple muscular abscesses, renal infarction, and septic arthritis of the right shoulder. He underwent computed tomography-guided drainage of the abscess. The abscess and blood cultures were positive for methicillin-susceptible S. aureus. The patient responded well to prolonged treatment with cefazolin and cephalexin and was discharged 12 weeks after initial admission.

An elderly gentleman self-presented to A+E with a 7-day history of significant and progressive left-sided neck pain, swelling and fevers, despite oral antibiotics from his general practitioner. Examination revealed a large left-sided neck mass involving levels 2-5 of the neck that was firm to palpate, with erythematous overlying skin.An urgent CT scan demonstrated a large collection throughout the length of the left sternocleidomastoid muscle (SCM), measuring 13×5.5×4 cm, with extensive adjacent inflammatory change. He was subsequently taken to theatre for washout and debridement, during which the collection was found to be loculated and isolated to the SCM, with surrounding structures spared.Postoperatively, he was managed with intravenous fluids and a total of 2 weeks of intravenous antibiotics. The wound partially dehisced during healing and the cavity was packed with flaminal and regularly dressed with input from the tissue viability team. This was then left to heal by secondary intention and the patient was followed up in clinic over the following weeks to ensure resolution.

Tubercular pyomyositis is a rare but distinct clinical entity which is difficult to diagnose especially in a patient with underlying autoimmune disease. The treatment is even more challenging if it is a multi-drug resistant strain. Here we report a patient with primary Sjögren\'s syndrome who presented with persistent inflammation of his right arm which was later diagnosed as multi-drug resistant tubercular pyomyositis. This case highlights the need for a high index of suspicion for tuberculosis in all cases of pyomyositis.

In patients with infectious symptoms and severe muscle pain, it is crucial to consider pyomyositis as a significant potential cause. A normal complete blood count should not exclude this possibility early in the course. Early advanced imaging modalities and blood cultures are crucial in narrowing the differential. Methicillin resistant Staphylococcus aureus is increasingly implicated.