Magnetic resonance imaging (MRI) revealed diffuse cellulitis and myositis of the deltoid and supraspinatus muscle concerning for myositis due to mRNA COVID-19 vaccine ; Magnetic resonance imaging (MRI) revealed diffuse cellulitis and myositis of the deltoid and supraspinatus muscle concerning for myositis due to mRNA COVID-19 vaccine; This is a literature report for the following literature source(s):   An 81-year-old man presented to the hospital with swelling, pain, and redness in the left arm that had started after he received his second dose of a messenger RNA (mRNA) vaccine. He had no history of allergies to medications and has had no adverse reactions to vaccinations in the past. He had received the first dose of a messenger RNA (mRNA) COVID-19 vaccine in the right arm 4 weeks ago, and he noticed redness and pain at the injection site, which resolved within 2 days. But 4 weeks later, after receiving the second dose of the mRNA vaccine, this time on the left arm, he noticed redness and pain at the injection site the following day. The redness and swelling continued to increase, involving the whole left arm and shoulder. His medical history included Parkinson disease, hypertension, paroxysmal atrial fi brillation, and giant cell arteritis, for which he was taking prednisone and tocilizumab. His blood pressure was 146/80 mm Hg, temperature 97.2°F (36.2°C), and heart rate 108 beats per minute. Physical examination revealed extensive erythema and tenderness involving the left upper extremity from the shoulder to the distal arm. Laboratory testing revealed the following: White blood cell count (4-11): 5 x10 9/l, Creatine kinase 236 U/L (reference range 35-232 U/L), Lactic acid 3.1 mmol/L (reference range 0.4-2 mmol/L), Aldolase 20.9 U/L (reference range 1.5- 8.1 U/L), C-reactive protein 6.3 mg/dL (reference range 0.0-0.9 mg/dL). Computed tomography (CT) of the left upper extremity showed proximal cellulitis and myositis of the deltoid muscle, and fasciitis was not excluded due to multicompartment findings. Magnetic resonance imaging (MRI) revealed diffuse cellulitis and myositis of the deltoid and supraspinatus muscle concerning for myositis due to mRNA COVID-19 vaccine. The patient was treated with intravenous vancomycin and piperacillin-tazobactam, and methylprednisolone 40 mg once a day, but the erythema and swelling of the left arm worsened, and on day 3 of hospitalization, he underwent local incision and drainage, which showed extensive edema without necrosis. Gram staining was negative for bacteria, and blood and wound culture did not grow any bacteria. On hospital day 4, repeat laboratory testing showed a creatine kinase level of 98 U/L and an aldolase level of 10.3 U/L. The swelling and redness of the left upper extremity improved, intravenous antibiotics were stopped, oral prednisolone 4 mg was started, and the patient was discharged on hospital day 7.; Sender's Comments: Based on the information currently available, a possible contributory role of the suspect drug to the reported events "Cellulitis and Myositis" cannot be completely excluded based on temporal association.   The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identifies as part of this review, as well as any appropriate action in response, will be promptly notifies to Regulatory Authorities, Ethics Committees and Investigators, as appropriate.,Linked Report(s) : US-PFIZER INC-PV202300054363 Same article/patient/drug and same event;