demyelinating neuropathy; his left arm is increasingly getting weaker; his shoulders have been getting weaker and weaker, but his left side is 10 times worse than his right side; anytime reaching above his head he almost can't do; difficult speech; loss of digital dexterity; feeling tired for the day; muscle atrophy of my left arm  (deltoid); This spontaneous case was reported by a dentist and describes the occurrence of NEUROPATHY PERIPHERAL (demyelinating neuropathy) in a 79-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 011A21A and 039K20A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     The patient's past medical history included Broken hip (broke his hip) in October 2020. Concurrent medical conditions included Atrial fibrillation. Concomitant products included FLECAINIDE, APIXABAN (ELIQUIS) and PRAVASTATIN for Atrial fibrillation.   On 27-Jan-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 24-Feb-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. In February 2021, the patient experienced MUSCLE ATROPHY (muscle atrophy of my left arm  (deltoid)). On an unknown date, the patient experienced NEUROPATHY PERIPHERAL (demyelinating neuropathy) (seriousness criterion medically significant), MUSCULAR WEAKNESS (his left arm is increasingly getting weaker), MUSCULOSKELETAL DISCOMFORT (his shoulders have been getting weaker and weaker, but his left side is 10 times worse than his right side), LOSS OF PERSONAL INDEPENDENCE IN DAILY ACTIVITIES (anytime reaching above his head he almost can't do), SPEECH DISORDER (difficult speech), FINE MOTOR SKILL DYSFUNCTION (loss of digital dexterity) and FATIGUE (feeling tired for the day). At the time of the report, NEUROPATHY PERIPHERAL (demyelinating neuropathy), MUSCULAR WEAKNESS (his left arm is increasingly getting weaker), MUSCULOSKELETAL DISCOMFORT (his shoulders have been getting weaker and weaker, but his left side is 10 times worse than his right side), LOSS OF PERSONAL INDEPENDENCE IN DAILY ACTIVITIES (anytime reaching above his head he almost can't do), MUSCLE ATROPHY (muscle atrophy of my left arm  (deltoid)), SPEECH DISORDER (difficult speech), FINE MOTOR SKILL DYSFUNCTION (loss of digital dexterity) and FATIGUE (feeling tired for the day) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In 2021, Blood magnesium: normal (normal) normal. In 2021, Magnetic resonance imaging: normal (normal) normal. In 2021, Spinal X-ray: normal (normal) normal.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   The patient reported that the diagnosis if demyelinating neuropathy was not a definitive diagnosis. Treatment medications were not provided by reporter.  Company comment This case concerns a 79-year-old male patient with previous medical history of atrial fibrillation, who experienced the unexpected event of Peripheral Neuropathy. The event occurred on an unknown date after receiving the second dose of mRNA-1273 (Moderna COVID-19 Vaccine). The rechallenge was not applicable since no information about the first dose was disclosed. The benefit-risk relationship of mRNA-1273 (Moderna COVID-19 Vaccine) is not affected by this report.   This case was linked to MOD-2021-276630 (Patient Link).   Most recent FOLLOW-UP information incorporated above includes: On 24-Sep-2021: Significant followup received. product event details updated which was missed to add in initial and events updated. case upgraded to serious.; Sender's Comments: This case concerns a 79-year-old male patient with previous medical history of atrial fibrillation, who experienced the unexpected event of Peripheral Neuropathy. The event occurred on an unknown date after receiving the second dose of mRNA-1273 (Moderna COVID-19 Vaccine). The rechallenge was not applicable since no information about the first dose was disclosed. The benefit-risk relationship of mRNA-1273 (Moderna COVID-19 Vaccine) is not affected by this report.