Acute transverse myelitis/Longitudinal extensive transverse myelitis; paresthesias in her bilateral toes; difficulty ambulating; burning sensation in back along the T8 dermatome; Constipation; increased severity of pain even to light touch in her lower extremities up to the knees; decreased sensation to proprioception; decreased sensation to vibration; Plantar reflexes were extensor bilaterally; decreased sensation light touch in upper and lower extremity; gait was hemiparetic; hyperintensities in the subcortical and periventricular white matter; chronic ischemic white matter changes; Urinary retention; Fatigue; muscle weakness; sensory changes; autonomic dysfunction; Lack of drug effect; This case was reported in a literature article and described the occurrence of myelitis transverse in a 73-year-old female patient who received Flu unspecified (Influenza vaccine) for prophylaxis.   Co-suspect products included DTPa (DTaP vaccine) for prophylaxis, valaciclovir hydrochloride (Valaciclovir) unknown for shingles and COVID-19 VACCINE (COVID 19 BOOSTER) for prophylaxis.   The patient's past medical history included hashimoto's thyroiditis, transient ischemic attack, mitral valve prolapse and shingles. Previously administered products included Covid 19.   On an unknown date, the patient received Influenza vaccine, DTaP vaccine, Valaciclovir at an unknown dose and frequency and COVID 19 BOOSTER. On an unknown date, less than 2 months after receiving Influenza vaccine and DTaP vaccine and not applicable after starting Valaciclovir, the patient experienced myelitis transverse (serious criteria hospitalization and GSK medically significant), paresthesia foot (serious criteria hospitalization), walking difficulty (serious criteria hospitalization), burning sensation (serious criteria hospitalization), constipation (serious criteria hospitalization), pain of lower extremities (serious criteria hospitalization), loss of proprioception (serious criteria hospitalization), decreased vibratory sense (serious criteria hospitalization), extensor plantar response (serious criteria hospitalization), hypoesthesia (serious criteria hospitalization), hemiplegic gait (serious criteria hospitalization), white matter hyperintensities (serious criteria hospitalization), white matter ischemia (serious criteria hospitalization and GSK medically significant), urinary retention (serious criteria hospitalization and GSK medically significant), fatigue (serious criteria hospitalization), muscle weakness (serious criteria hospitalization), sensory disturbance (serious criteria hospitalization), autonomic dysfunction (serious criteria hospitalization) and lack of drug effect. The patient was treated with methylprednisolone and operations and procedures (Plasma Exchange). The action taken with Valaciclovir was unknown. On an unknown date, the outcome of the myelitis transverse, paresthesia foot, walking difficulty, burning sensation, constipation, pain of lower extremities, loss of proprioception, decreased vibratory sense, extensor plantar response, hypoesthesia, hemiplegic gait, white matter hyperintensities, white matter ischemia, urinary retention, fatigue, muscle weakness, sensory disturbance and autonomic dysfunction were recovering/resolving and the outcome of the lack of drug effect was unknown.   The reporter considered the myelitis transverse, paresthesia foot, walking difficulty, burning sensation, constipation, pain of lower extremities, loss of proprioception, decreased vibratory sense, extensor plantar response, hypoesthesia, hemiplegic gait, white matter hyperintensities, white matter ischemia, urinary retention, fatigue, muscle weakness, sensory disturbance and autonomic dysfunction to be related to Influenza vaccine and DTaP vaccine.     Additional Information: GSK Receipt Date: 10-Oct-2022 Author's comment:  The patient had a medical history significant for Hashimoto's thyroiditis, transient ischemic attack, and mitral valve prolapse. The patient had Shingles in her past, and she was started on valacyclovir with no improvement. Further history revealed she had been hiking a few weeks prior and was unsure if she had any tick bites. The patient presented to the emergency department with a complaint of paresthesias in her bilateral toes and difficulty ambulating. The patient's symptoms began as a burning sensation in her back along the T8 dermatome, prompting her to go to an urgent care center a few days later. There was a concern for shingles flare-up due to a history of shingles. She complained of constipation but denied fever, chills, urinary or bowel incontinence, vision changes, myalgias, arthralgias, or rashes. Her symptoms continued to worsen, with increased severity of pain even to light touch in her lower extremities up to the knees.  She was vaccinated for COVID-19 and received her booster shot four days prior to admission. She had also recently received influenza and TDaP vaccines about a month prior to her symptom onset. Upon arrival to the emergency room, she was afebrile. At the T8 hemisensory level, there was decreased sensation to proprioception, vibration, and light touch in the left upper and lower extremity. Her reflexes were 3+ in bilateral lower extremities and 2+ in bilateral upper extremities. Plantar reflexes were extensor bilaterally. Her gait was unsteady and hemiparetic. Brain magnetic resonance imaging (MRI) showed scattered T2/fluid-attenuated inversion recovery (FLAIR) hyperintensities in the subcortical and periventricular white matter, interpreted to be chronic ischemic white matter changes. There was no mass effect or midline shift. T2-weighted sequence MRI of the spine was remarkable for an abnormal diffusely increased T2 signal with contrast enhancement of the lower cervical spine and most of the thoracic spine involving greater than two-thirds of the cross-sectional area. In the lumbar spine, there was mild grade 1 retrolisthesis of L1 in relation to L2 and disc bulge at the L4-L5 level encroaching upon the descending bilateral L5 nerve roots. Lumbar puncture was also performed. Based on her spine MRI findings, she was diagnosed with acute transverse myelitis (ATM). Due to the contiguous involvement of greater than three vertebrae, she was further categorized as having longitudinal extensive transverse myelitis (LETM). She was treated with intravenous methylprednisolone 1,000 mg daily for five days, alternating with plasma exchange (PLEX) therapy every other day. Normally, one of these treatments alone would have sufficed; however, they were started simultaneously due to the onset of urinary retention. She had frequent neurology checks every four hours and bladder scans every six hours. A Foley catheter was placed due to urinary retention of more than 800 mL, and she worked with physical therapy daily. She experienced an improvement in her weakness of the right lower extremity and was able to have the same strength in both legs by the end of treatment. Her left upper and lower limb sensory changes also improved and were back to baseline by the end of her treatment. She had a repeat spine MRI eight days after the initial imaging, which showed nearly complete resolution of the abnormal T2 cord signal at the C7 level and significantly improved signal in the thoracic spine that decreased from eight days prior. Upon discharge, she was sent to an acute rehabilitation facility and recommended to follow up with neurology outpatient. "Furthermore, having an underlying autoimmune disease could have been a predisposing factor to either postinfectious or post-vaccine autoimmune phenomenon. The exact mechanism behind this type of abnormal immune response is unknown; however, when the body attacks its own cells, there will be a less effective response to infections and, vice versa, more sensitivity to potential vaccine adverse effects. Since a host's response to a vaccine is originally made to protect immunity, vaccines can work in similar ways to how infectious agents induce autoimmunity. Although the exact mechanism by which the postinfectious or post-vaccine autoimmunity phenomenon occurs is unknown, there are many proposed pathways. The temporal association between vaccines and the onset of symptoms can vary from one to two weeks to as late as two months. Some of the most common vaccines associated with ATM are influenza, hepatitis B, measles, mumps, and rubella (MMR), TDaP, and human papillomavirus (HPV). This has led to the bigger question about the recurrence risk and the safety of using vaccines in these patients. "This case of acute transverse myelitis shows a patient with several risk factors including autoimmune disease (Hashimoto's thyroiditis), recent vaccinations, and possible viral infection exposure. In cases where possible vaccine adverse effects are suspected, it is important for these patients to be closely monitored during the course of their disease and monitor for potential recurrence". Additional supportive information: The article corresponding to this case is not available for regulatory submission due to copyright restriction.