multifocal acquired demyelinating sensory and motor neuropathy; Hemolytic anemia; This literature-non-study case was reported in a literature article and describes the occurrence of CHRONIC INFLAMMATORY DEMYELINATING POLYRADICULONEUROPATHY (multifocal acquired demyelinating sensory and motor neuropathy) and HAEMOLYTIC ANAEMIA (Hemolytic anemia) in a 23-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 prophylaxis.       No Medical History information was reported.    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 CHRONIC INFLAMMATORY DEMYELINATING POLYRADICULONEUROPATHY (multifocal acquired demyelinating sensory and motor neuropathy) (seriousness criterion medically significant) and HAEMOLYTIC ANAEMIA (Hemolytic anemia) (seriousness criterion medically significant). At the time of the report, CHRONIC INFLAMMATORY DEMYELINATING POLYRADICULONEUROPATHY (multifocal acquired demyelinating sensory and motor neuropathy) was resolving and HAEMOLYTIC ANAEMIA (Hemolytic anemia) had resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Alanine aminotransferase: 107 U/L Elevated after IVIg treatment. On an unknown date, Antibody test: anti-MAG antibodies-unremarkable. On an unknown date, Aspartate aminotransferase: 54 U/L Elevated after IVIg treatment. On an unknown date, Blood bilirubin unconjugated: 0.8 mg/dl elevated. On an unknown date, Blood grouping: AB negative, Rh negative.. On an unknown date, Blood lactate dehydrogenase: Normal. On an unknown date, CSF cell count: no pleocytosis. On an unknown date, CSF protein (15-45 mg/dl): 45 mg/dl borderline. On an unknown date, Coombs direct test: Negative. On an unknown date, Electroneuromyography: The needle electromyography portion of the electrodiagnostic study was normal. On an unknown date, Haemoglobin: 15 g/dL baseline, 12.3 g/dL five days after IVIg treatment and 10.6 g/dL eight days after IVIg treatment. On an unknown date, Haptoglobin: less than 8 mg/dL- Low. On an unknown date, Immunoelectrophoresis: unremarkable. On an unknown date, Immunology test: unremarkable. On an unknown date, Light chain analysis: unremarkable. On an unknown date, Nerve conduction studies: nerve conduction studies (NCS) showed normal sensory nerve action potentials (SNAP) in absolute terms, but amplitudes were asymmetric in two nerves (sural: right 11.6uV and left 21.5uV, median: right 18.4uV and left 41.0uV). Compound muscle action potentials (CMAP) had slowed conduction velocities in multiple nerves, several with associated conduction block. The peroneal extensor digitorum brevis CMAP had particularly slowed conduction velocities with conduction block. The left median and tibial F-wave latencies were prolonged.  Although the NCS abnormalities were much more striking in motor nerves, the asymmetric SNAPs along with the patient's sensory symptoms and deficits on examination suggest sensorimotor involvement. Taken together, NCS demonstrated a generalized, non-length-dependent, sensorimotor, demyelinating polyneuropathy. On an unknown date, Neurological examination: notable for distal weakness of both upper and lower extremities, more pronounced on the left. Shoulder abduction, elbow extension and flexion, and wrist extension and flexion strength were graded 5/5 bilaterally using the Medical Research Council (MRC) scale, finger abduction (interosseous) and thumb abduction (abductor pollicis brevis) were 4/5 bilaterally, hip flexion, knee extension and flexion were 5/5 bilaterally, ankle dorsiflexion was 4/5 bilaterally, ankle plantarflexion was 5/5 bilaterally, toe extension was 1/5 on the left and 4/5 on the right, and toe flexion was 5/5 bilaterally. He could march on his toes but not on his heels. On an unknown date, Reflex test: absent throughout. On an unknown date, Reticulocyte count: 2.2 % elevated. On an unknown date, Romberg test: Romberg's sign were absent. On an unknown date, Skin test: Sensation to pinprick was decreased distally in both upper and lower extremities with 8 seconds timed vibration sensation at bilateral great toes, while proprioception was intact.. On an unknown date, Urine analysis: unremarkable. On an unknown date, Vascular endothelial growth factor assay: unremarkable.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter did not provide any causality assessments.   Concomitant medication not reported.  The patient had received the Moderna vaccine booster dose and three days later noticed left thumb numbness and tingling that spread throughout his hand, followed a month later by sensory changes in both legs and left leg weakness. Previously patient was a lacrosse player and lost the ability to run after vaccination. Patient denied neck or low back pain and any preceding illness.  The patient was presented with numbness, tingling, and weakness in his extremities progressing over four months. Patient underwent neurologic examination and nerve conduction studies (NCS).   Patient's NCS met diagnostic criteria of Chronic inflammatory demyelinating polyneuropathy (CIDP) by Academy of Neurology. This was followed by laboratory studies corresponding to the differential diagnosis.  The patient did not have toxic exposures, a contributory family history, or systemic symptoms suggestive of a plasma cell dyscrasia. Patient's neuropathy was best characterized as sensorimotor, asymmetric, and subacute. These elements were most consistent with a diagnosis of multifocal acquired demyelinating sensory and motor neuropathy (MADSAM).  Patient received treatment with 2g per kg of intravenous immunoglobulins (IVIg) administered over two days. However, after noticing dark-colored urine and fatigue which suggested hemolytic anemia, the patient received high-dose steroids, and the long-term treatment was switched to subcutaneous immunoglobulin. Patient did not experience further adverse effects and had gradual improvement in motor strength and sensory symptoms.  Author stated that there was possibility that a vaccination unmasks an underlying, previously asymptomatic autoimmune disorder rather than cause it.  Company comment: This literature-non-study case concerns a male patient aged 23 years with no  preceding illness reported, who experienced the unexpected serious (medically significant) events of Chronic inflammatory demyelinating polyradiculoneuropathy(CIDP) (reported as multifocal acquired demyelinating sensory and motor neuropathy(MADSAM) and AESI) and Haemolytic anaemia, after booster dose of mRNA-1273 vaccine in covid-19 vaccination series. Patient presented with numbness, tingling, and weakness in his extremities progressing over four months. He initially noticed left thumb numbness and tingling that spread throughout his hand, followed a month later by sensory changes in both legs and left leg weakness. He denied neck or low back pain and had received the Moderna vaccine booster three days prior to symptom onset. His initial neurologic examination was notable for distal weakness of both upper and lower extremities, more pronounced on the left. Sensation to pinprick was decreased distally in both upper and lower extremities, while proprioception was intact. Romberg's sign was absent. Reflexes were absent throughout. The combination of motor weakness, sensory abnormalities, and areflexia a disorder of the lower motor neurons, simultaneous upper and lower extremity involvement narrows the localization to the peripheral nerves, with a non-length-dependent pattern suggestive of an inflammatory polyneuropathy. Although the Nerve conduction study (NCS) abnormalities were much more striking in motor nerves, the asymmetric SNAPs along with the patient's sensory symptoms and deficits on examination suggest sensorimotor involvement. NCS demonstrated a generalized, non length-dependent, sensorimotor, demyelinating polyneuropathy. Patient's NCS met diagnostic criteria for multifocal CIDP in the 2021 revised Academy of Neurology/Peripheral Nerve Society guidelines. Patient did not have toxic exposures, a contributory family history, or systemic symptoms suggestive of a plasma cell dyscrasia. He had unremarkable serum electrophoresis (SPEP), immunofixation (IFE), free light chains, anti-MAG antibodies, and vascular endothelial growth factor. Given the non-contributory history and normal serum studies, CIDP or a CIDP variant was strongly considered. Cerebrospinal fluid (CSF) studies revealed a borderline protein of 45mg/dL with no pleocytosis. This patient's neuropathy was best characterized as sensorimotor, asymmetric, and subacute which was most consistent with a diagnosis of MADSAM. Patient was started on 2g/kg of intravenous immunoglobulins (IVIg) administered over two days. Three days after the initial dose, he noticed dark-colored urine and fatigue, five days after IVIg infusions, hemoglobin was 12.3g/dL (baseline of 15g/dL), which subsequently dropped to 10.6g/dL. Aspartate transaminase (AST) and alanine transaminase (ALT) were raised. Down trending hemoglobin following IVIg suggests hemolytic anemia, a rare complication which is most common in non-O blood group patients (patient-AB negative). An elevated reticulocyte index (2.2%), elevated indirect bilirubin (0.8mg/dL), and low haptoglobin supported the diagnosis. Direct antiglobulin test (DAT) was negative, a finding in 12.5% of cases of hemolytic anemia with unclear mechanism. Patient received high-dose steroids, and the long-term treatment was switched to subcutaneous immunoglobulin. He did not experience further adverse effects and had gradual improvement in motor strength and sensory symptoms. Author concludes that vaccination possibly unmasks an underlying, previously asymptomatic autoimmune disorder rather than cause it. The benefit-risk relationship of mRNA-1273 is not affected by this report.   Most recent FOLLOW-UP information incorporated above includes: On 04-Jan-2023: Live follow up received by safety on 04-Jan-2023 has email with full text article and contains significant information. Reporter information, Literature information, lab data, treatment drug and event details updated,; Sender's Comments: This literature-non-study case concerns a male patient aged 23 years with no  preceding illness reported, who experienced the unexpected serious (medically significant) events of Chronic inflammatory demyelinating polyradiculoneuropathy(CIDP) (reported as multifocal acquired demyelinating sensory and motor neuropathy(MADSAM) and AESI) and Haemolytic anaemia, after booster dose of mRNA-1273 vaccine in covid-19 vaccination series. Patient presented with numbness, tingling, and weakness in his extremities progressing over four months. He initially noticed left thumb numbness and tingling that spread throughout his hand, followed a month later by sensory changes in both legs and left leg weakness. He denied neck or low back pain and had received the Moderna vaccine booster three days prior to symptom onset. His initial neurologic examination was notable for distal weakness of both upper and lower extremities, more pronounced on the left. Sensation to pinprick was decreased distally in both upper and lower extremities, while proprioception was intact. Romberg's sign was absent. Reflexes were absent throughout. The combination of motor weakness, sensory abnormalities, and areflexia a disorder of the lower motor neurons, simultaneous upper and lower extremity involvement narrows the localization to the peripheral nerves, with a non-length-dependent pattern suggestive of an inflammatory polyneuropathy. Although the Nerve conduction study (NCS) abnormalities were much more striking in motor nerves, the asymmetric SNAPs along with the patient's sensory symptoms and deficits on examination suggest sensorimotor involvement. NCS demonstrated a generalized, non length-dependent, sensorimotor, demyelinating polyneuropathy. Patient's NCS met diagnostic criteria for multifocal CIDP in the 2021 revised Academy of Neurology/Peripheral Nerve Society guidelines. Patient did not have toxic exposures, a contributory family history, or systemic symptoms suggestive of a plasma cell dyscrasia. He had unremarkable serum electrophoresis (SPEP), immunofixation (IFE), free light chains, anti-MAG antibodies, and vascular endothelial growth factor. Given the non-contributory history and normal serum studies, CIDP or a CIDP variant was strongly considered. Cerebrospinal fluid (CSF) studies revealed a borderline protein of 45mg/dL with no pleocytosis. This patient's neuropathy was best characterized as sensorimotor, asymmetric, and subacute which was most consistent with a diagnosis of MADSAM. Patient was started on 2g/kg of intravenous immunoglobulins (IVIg) administered over two days. Three days after the initial dose, he noticed dark-colored urine and fatigue, five days after IVIg infusions, hemoglobin was 12.3g/dL (baseline of 15g/dL), which subsequently dropped to 10.6g/dL. Aspartate transaminase (AST) and alanine transaminase (ALT) were raised. Down trending hemoglobin following IVIg suggests hemolytic anemia, a rare complication which is most common in non-O blood group patients (patient-AB negative). An elevated reticulocyte index (2.2%), elevated indirect bilirubin (0.8mg/dL), and low haptoglobin supported the diagnosis. Direct antiglobulin test (DAT) was negative, a finding in 12.5% of cases of hemolytic anemia with unclear mechanism. Patient received high-dose steroids, and the long-term treatment was switched to subcutaneous immunoglobulin. He did not experience further adverse effects and had gradual improvement in motor strength and sensory symptoms. Author concludes that vaccination possibly unmasks an underlying, previously asymptomatic autoimmune disorder rather than cause it. The benefit-risk relationship of mRNA-1273 is not affected by this report.