I experienced a sudden sharp pain - like an extended cramp in my left lower leg; sonogram was performed and it revealed that she has a popliteal vein aneurysm in my left lower leg; sudden sharp pain on her left lower calf/A few days later, I experienced a sudden sharp pain - like an extended cramp in my left lower leg; Itchy; swelling on the arm where she received the vaccine - left arm; Red; my left upper arm broke out in a red rash that was raised, swollen and painful; Swollen raised red rash along left arm from elbow to shoulder/my left upper arm broke out in a red rash that was raised, swollen and painful; This spontaneous case was reported by a consumer and describes the occurrence of VENOUS ANEURYSM (sonogram was performed and it revealed that she has a popliteal vein aneurysm in my left lower leg), PAIN IN EXTREMITY (sudden sharp pain on her left lower calf/A few days later, I experienced a sudden sharp pain - like an extended cramp in my left lower leg), VACCINATION SITE PRURITUS (Itchy), VACCINATION SITE SWELLING (swelling on the arm where she received the vaccine - left arm) and VACCINATION SITE ERYTHEMA (Red) in a 40-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 027C21A and 025B21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Concurrent medical conditions included Von Willebrand's disease (A clotting disorder due to lack of clotting factor 8.) and Drug allergy (Salicylates). Concomitant products included VITAMIN C [ASCORBIC ACID] from 01-Jan-2000 to an unknown date and MAGNESIUM POWDER [ASCORBIC ACID;CALCIUM PANTOTHENATE;CYANOCOBALAMIN;FOLIC ACID;LEVOCARNITINE TARTRATE;LEVOGLUTAMIDE;MAGNESIUM AMINO ACID CHELATE;MAGNESIUM ASPARTATE DIHYDRATE;MAGNESIUM CITRATE;MAGNESIUM PHOSPHATE;NICOTINAMIDE;POTASSIUM PHOSPHATE MONO from 01-Jan-2019 to an unknown date for an unknown indication.   On 02-Apr-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 05-May-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On 13-Feb-2021, the patient experienced RASH ERYTHEMATOUS (Swollen raised red rash along left arm from elbow to shoulder/my left upper arm broke out in a red rash that was raised, swollen and painful). On 12-Apr-2021, the patient experienced VACCINATION SITE PRURITUS (Itchy), VACCINATION SITE SWELLING (swelling on the arm where she received the vaccine - left arm), VACCINATION SITE ERYTHEMA (Red) and VACCINATION SITE PAIN (my left upper arm broke out in a red rash that was raised, swollen and painful). On 16-Apr-2021, the patient experienced VENOUS ANEURYSM (sonogram was performed and it revealed that she has a popliteal vein aneurysm in my left lower leg) and PAIN IN EXTREMITY (sudden sharp pain on her left lower calf/A few days later, I experienced a sudden sharp pain - like an extended cramp in my left lower leg). On an unknown date, the patient experienced MUSCLE SPASMS (I experienced a sudden sharp pain - like an extended cramp in my left lower leg). On 20-Feb-2021, RASH ERYTHEMATOUS (Swollen raised red rash along left arm from elbow to shoulder/my left upper arm broke out in a red rash that was raised, swollen and painful) had resolved. At the time of the report, VENOUS ANEURYSM (sonogram was performed and it revealed that she has a popliteal vein aneurysm in my left lower leg) had not resolved and PAIN IN EXTREMITY (sudden sharp pain on her left lower calf/A few days later, I experienced a sudden sharp pain - like an extended cramp in my left lower leg), VACCINATION SITE PRURITUS (Itchy), VACCINATION SITE SWELLING (swelling on the arm where she received the vaccine - left arm), VACCINATION SITE ERYTHEMA (Red), VACCINATION SITE PAIN (my left upper arm broke out in a red rash that was raised, swollen and painful) and MUSCLE SPASMS (I experienced a sudden sharp pain - like an extended cramp in my left lower leg) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Magnetic resonance imaging head: normal (normal) normal. On an unknown date, Ultrasound scan: abnormal (abnormal) Diagnosed with popliteal vein aneurysm..     For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter did not provide any causality assessments.   Treatment medications was not provided.   Most recent FOLLOW-UP information incorporated above includes: On 20-Jul-2021: Significant Follow-up Second dose information was given