Acute flaccid myelitis presumably caused by coxsackie virus A10

Enterovirus-D68 (EV-D68) has been presumed to be a major cause of acute flaccid myelitis (AFM) since its cluster in 2014.1 Coxsackie virus (CV)-A10 causes hand-foot-mouth disease, herpangina, and non-specific febrile illnesses, whereas neurological complications are rare. We encountered a child with AFM during an outbreak of EV-D68 infection in autumn 2018 and CV-A10 RNA was detected from her stool. The patient was a previously healthy 4-year-old girl. In September 2018, she developed fever and cough. Five days later, right-dominant weakness was noted in both arms. She also had a pain in the neck. She was admitted to our hospital 2 days after the onset of weakness. On admission, the manual muscle test (MMT) score was 0–1 in the right shoulder and elbow, 2–3 in the right wrist, and 4 in the left arm. No weakness was detected in either leg. The deep tendon reflexes were weak or absent in both arms, but were maintained in both legs. The cranial nerve functions were normal and no sensory disorders were observed. Neurogenic bladder / bowel was not seen. Laboratory testing revealed a normal white blood cell count. Cerebral spinal fluid (CSF) analysis showed pleocytosis of 227 cells/μL with a normal protein level of 57 mg/dL. MRI 3 days after the onset of weakness showed longitudinal high intensities spanning from the pons to the entire cervical spine (Fig. 1a). The lower level of the lesion was uncertain because the thoraco-lumbar spine was not evaluated. The parenchymal spinal lesion was anterior horn dominant (Fig. 1b), involving the gray matter. Head MRI revealed lesions in the medulla oblongata and dorsal pons (Fig. 1c,d). The patient was diagnosed with AFM and treated with intravenous immunoglobulin and methylprednisolone pulse treatments beginning the day after admission. The limb paralysis worsened after the treatment. Three days after admission, she could not sit without support. MRI 9 days after the onset of weakness showed that the longitudinal lesions in the cervical spine were less obvious (Fig. 1e) with contrast enhancement in the anterior roots of the cauda equina (Fig. 1f). The weakness subsequently improved, gradually. At 2 months after the onset, the MMT score was 5 in both hands, 4 in the left forearm, and 2 in the right forearm and both arms. Nerve transfer in the right upper limb was performed 6 months after discharge. At 1 year after discharge, the MMT scores in the right forearm and arm improved to 2–3. We collected throat swab, urine, stool, blood, and CSF specimens from the patient 3 days after the onset of limb weakness for virus detection, including enteroviruses, herpesviruses, and adenoviruses. CV-A10 RNA was detected from the stool by PCR, but not from any other specimens. EV-D68 RNA was not detected from any specimens. Informed consent was obtained from the patient's parents for publication. This study was approved by the institutional review board. Acute flaccid myelitis has been defined as acute-onset flaccid limb weakness, with imaging showing spinal cord grey matter lesions suggestive of anterior myelitis.2 Cerebrospinal fluid analysis often reveals pleocytosis in children with AFM.1, 3 Our patient had all these features and was diagnosed with AFM. The neurological symptoms and their time course in our patient were similar to those of AFM during the outbreak of EV-D68 infection.1, 3 The interval between the onset of fever and limb weakness was 5 days. The asymmetric flaccid limb paralysis without obvious sensory disturbance or neurogenic bladder / bowel was suggestive of anterior horn involvement. The limb weakness worsened rapidly, reaching a plateau within 1 day. It is notable that several viruses other than EV-D68 can be detected in patients with AFM. Ayers et al. reported that CV-A10 was detected from stool/rectal swab in 1 of 218 children with confirmed or probable AFM.4 Suresh et al. identified CV-A10 was identified in 30 of 5,450 specimens from patients with acute flaccid paralysis.5 This implies that CV-A10 is infrequently isolated form patients with acute flaccid paralysis. Nevertheless, they stated that acute flaccid paralysis related to CV-A10 was not found in any case reports or case series. Our report will be useful for understanding the clinical features of AFM related to CV-A10. Regular virologic surveillance is important for identifying causative agents and their trends in relation to that of AFM, as there is a possibility that a novel neurotropic enterovirus may emerge as a major cause of paralytic diseases. This work was supported by the Health and Labor Sciences Research Grant from the Ministry of Health, Labor and Welfare of Japan (H28-Shinkogyosei-Ippan-007). The authors declare no conflict of interest. F.B. and A.O. contributed to the conception and design of this study. S.S. performed virological studies. F.B., M.H., and S.M. collected clinical data. F.B. drafted the manuscript. A.O. critically reviewed the manuscript and supervised the whole study process. All authors read and approved the final manuscript.