Acquired factor inhibitor deficiency; This literature-non-study case was reported in a literature article and describes the occurrence of COAGULATION FACTOR DEFICIENCY (Acquired factor inhibitor deficiency) in a 77-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination.    Concurrent medical conditions included Hypertension, Obesity and Steroid psychosis.    On an unknown date, the patient received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On an unknown date,  after starting mRNA-1273 (Moderna COVID-19 Vaccine), the patient experienced COAGULATION FACTOR DEFICIENCY (Acquired factor inhibitor deficiency) (seriousness criterion hospitalization). The patient was treated with CRYOPRECIPITATE for Adverse event, at a dose of 1 dosage form; VITAMIN K NOS for Adverse event, at a dose of 1 dosage form; FACTOR X (STUART PROWER FACTOR) for Adverse event, at a dose of 2500 international unit; PREDNISONE for Adverse event, at a dose of 1 dosage form and RITUXIMAB for Adverse event, at a dose of 1 dosage form once a week. At the time of the report, COAGULATION FACTOR DEFICIENCY (Acquired factor inhibitor deficiency) had resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Coagulation factor X level: <2% (Low) low at <2%. and 132% (normal) 132 %. On an unknown date, Haemoglobin: drop from baseline of 13.8 to 11.8 to 8.2 g/dl. (Low) Drop from baseline of 13.8 to 11.8 to 8.2 g/dL.. On an unknown date, Laboratory test: elevated pt 130 sec, ptt 108.7 (High) Significant coagulopathy, with elevated PT 130 sec, PTT 108.7. On an unknown date, Prothrombin time: 1:1 mix pt 22.7 sec; normal 9.4-12.5 sec Mixing study of the prolonged prothrombin time mainly demonstrates an inhibitory pattern, with incomplete correction. (1:1 mix PT 22.7 sec; normal 9.4-12.5 sec)..     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter considered COAGULATION FACTOR DEFICIENCY (Acquired factor inhibitor deficiency) to be related.    Concomitant medications were not reported.  The patient presented to the hospital with epigastric pain, hematochezia, hematuria, epistaxis, and significant bruising without trauma. Laboratory studies showed hemoglobin drop from baseline of 13.8 to 11.8 to 8.2 g/dL. Significant coagulopathy, with elevated PT 130 sec, PTT 108.7. All factor levels were normal except Factor X levels low at <2%. Mixing study of the prolonged prothrombin time mainly demonstrates an inhibitory pattern, with incomplete correction. (1:1 mix PT 22.7 sec; normal 9.4-12.5 sec). Bethesda titers could not be demonstrated. No neoplastic or rheumatologic etiology of her inhibitor was found. She was given cryoprecipitate and vitamin K with no improvement in her coagulation studies. She received factor X infusion for 3 doses 2500 units during day 3 of her hospitalization. She was treated with prednisone and weekly rituximab with complete normalization of her Factor X levels at 132%.  This is a literature-non-study case concerning  a  77-year-old, female patient with no relevant medical history, who experienced the unexpected serious events of Coagulation factor deficiency. The events occurred on an unknown day after the second dose of mRNA-1273 COVID 19 Vaccine. Patients laboratory test: Coagulation factor X level, Hemoglobin low results and elevated results of PT, PTT The event were reported as resolved. Patient was treated with treated with prednisone and weekly rituximab. The benefit-risk relationship of mRNA-1273 COVID 19 Vaccine, is not affected by this report.   This case was linked to MOD-2022-512280 (Patient Link).; Sender's Comments: This is a literature-non-study case concerning  a  77-year-old, female patient with no relevant medical history, who experienced the unexpected serious events of Coagulation factor deficiency. The events occurred on an unknown day after the second dose of mRNA-1273 COVID 19 Vaccine. Patients laboratory test: Coagulation factor X level, Hemoglobin low results and elevated results of PT, PTT The event were reported as resolved. Patient was treated with treated with prednisone and weekly rituximab. The benefit-risk relationship of mRNA-1273 COVID 19 Vaccine, is not affected by this report.