Wrist Extensor Tenosynovitis; painful nodules along her left upper extremity and torso; potential inflammatory arthritis; Bone marrow edema; Pericapsular edema; This literature-non-study case was reported in a literature article and describes the occurrence of TENOSYNOVITIS (Wrist Extensor Tenosynovitis) in a 54-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 prophylaxis. The occurrence of additional non-serious events is detailed below.   LITERATURE REFERENCE.    The patient's past medical history included Tenosynovectomy (approximately 7 months after the initial onset of her symptoms.).    On an unknown date, the patient received dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On an unknown date, the patient experienced TENOSYNOVITIS (Wrist Extensor Tenosynovitis) (seriousness criterion medically significant), NODULE (painful nodules along her left upper extremity and torso), ARTHRITIS (potential inflammatory arthritis), BONE MARROW OEDEMA (Bone marrow edema) and OEDEMA PERIPHERAL (Pericapsular edema). The patient was treated with Surgery (Occupational therapy and home exercise plan) for Tenosynovitis. At the time of the report, TENOSYNOVITIS (Wrist Extensor Tenosynovitis), ARTHRITIS (potential inflammatory arthritis), BONE MARROW OEDEMA (Bone marrow edema) and OEDEMA PERIPHERAL (Pericapsular edema) outcome was unknown and NODULE (painful nodules along her left upper extremity and torso) was resolving.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Finkelstein test: Negative. On an unknown date, Magnetic resonance imaging: Magnetic resonance imaging (MRI) of the left wrist was obtained 109 days after the vaccine booster administration, demonstrating severe tenosynovitis of the fourth extensor compartment and mild tenosynovitis of the second extensor compartment, as well as pericapsular edema, bone marrow edema, and cystic/erosive changes consistent with potential inflammatory arthritis. and repeat MRI of the left wrist was obtained demonstrating the recurrence of her synovitis.. On an unknown date, Pathology test: Surgical pathology of the excised tenosynovium demonstrated synovial hyperplasia with mild chronic inflammation. and Surgical pathology of the excised tenosynovium from the second surgical excision demonstrated fibrosis and reactive changes.. On an unknown date, Physical examination: multiple palpable fluid-filled nodules over the dorsum of the wrist at the extensor tendon sheath were observed. No signs of erythema or infection existed.   Patient was neurovascularly intact with intact sensation to light touch over the median, radial, and ulnar nerve distributions and appropriate capillary refill of the fingertips..     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter considered NODULE (painful nodules along her left upper extremity and torso), ARTHRITIS (potential inflammatory arthritis), BONE MARROW OEDEMA (Bone marrow edema) and OEDEMA PERIPHERAL (Pericapsular edema) to be related. No further causality assessment was provided for TENOSYNOVITIS (Wrist Extensor Tenosynovitis).    Concomitant and treatment medications were not reported.  Patient presented to clinic with complaint of multiple months of painful nodules over the dorsum of her left wrist. Immediately after administration of the booster beginning on the day of injection, she developed painful nodules that tracked along her entire left upper extremity and her torso. Many of the nodules subsided over the following 3 months before this clinic presentation, except for those at the dorsum of the left wrist.   Reported that these nodules persisted and were painful with any active or passive range of motion of her left wrist and extension of the fingers.  Multiple palpable fluid-filled nodules over the dorsum of the wrist at the extensor tendon sheath were observed.  Patient elected to pursue tenosynovectomy of the left wrist extensor compartments.  The nodules were marked, and an incision was made along the dorsum of the hand between the third and fourth extensor compartments. Dissection to the extensor retinaculum revealed tenosynovium "bulging" underneath the retinaculum. The extensor retinaculum was removed, the extensor pollicis longus was released and transposed, and the posterior interosseous nerve was resected. The exposed tenosynovium was excised from the dorsal wrist and along the tendons, measuring 4 x 3 x 2 cm.  At follow-up visit, the patient reported overall pain improvement, but with continued difficulty with wrist range of motion. She was referred to occupational therapy starting at 6 weeks after surgery, and she attended 13 sessions over 10 weeks. At the 3-month follow-up, she reported continued pain and swelling over the wrist.  Dissection was made through the old incision, and synovitis was again encountered and excised from the extensor tendon.  After surgery, the patient attended 11 occupational therapy sessions over 11 weeks and was discharged with recommendations for a home exercise plan.  Company Comment: This is a literature non-study case concerning a 54-year-old female patient, with no medical history of rheumatic disease or trauma to the upper extremities, who experienced the unexpected and serious (due to medically significant) event of Tenosynovitis, and the unexpected and non-serious AESI of Arthritis, which occurred after mRNA-1273 vaccine, administered as first booster shot within COVID-19 vaccination schedule. As reported, patient presented to the outpatient clinic with a chief complaint of multiple months of painful nodules over the dorsum of her left wrist. She received her first booster shot of mRNA-1273, 3 months before this presentation in her left arm. Immediately after administration of the booster beginning on the day of injection, she developed painful nodules that tracked along her entire left upper extremity and her torso. Many of the nodules subsided over the following 3 months before this clinic presentation, except for those at the dorsum of the left wrist. She reported that these nodules persisted and were painful with any active or passive range of motion of her left wrist and extension of the fingers. On clinical examination, multiple palpable fluid-filled nodules over the dorsum of the wrist at the extensor tendon sheath were observed. No signs of erythema or infection existed. Finkelstein's test was negative. Magnetic resonance imaging (MRI) of the left wrist was obtained 109 days after the vaccine, demonstrating severe tenosynovitis of the fourth extensor compartment and mild tenosynovitis of the second extensor compartment, as well as pericapsular edema, bone marrow edema, and cystic/erosive changes consistent with potential inflammatory arthritis. Given the severity of her symptoms and advanced imaging findings consistent with inflammatory tissue, the patient elected to pursue tenosynovectomy of the left wrist extensor compartments (7 months after the initial onset of her symptoms). Surgical pathology of the excised tenosynovium demonstrated synovial hyperplasia with mild chronic inflammation. At her first follow-up visit, the patient reported overall pain improvement, but with continued difficulty with wrist range of motion. She was referred to occupational therapy. At the 3-month follow-up, she reported continued pain and swelling over the wrist, and a repeat MRI of the left wrist was obtained demonstrating the recurrence of her synovitis. She was subsequently taken back to the operating room, where dissection was made through the old incision, and synovitis was again encountered and excised from the extensor tendon. Surgical pathology of the excised tenosynovium from the second surgical excision demonstrated fibrosis and reactive changes. The benefit-risk relationship of mRNA-1273 vaccine is not affected by this report.