Objective: To summarize the clinical characteristics of a patient with cerebellar ataxia, areflexia, pes cavus, optic atrophy and sensorineural hearing loss (CAPOS) syndrome, followed by relative literature review. Methods: The medical history, physical examination and results of relative auxiliary examinations were collected from a CAPOS syndrome patient, who was definitely diagnosed by gene detection. Results: The patient was a 20-year-old male, complaining of poor coordination for 19 years, impaired vision for 15 years and hearing loss for 13 years. When he was eleven months old, weakness of four limbs happened after diarrhea but recovered spontaneously a few days later. Then his poor coordination was discovered. His vision has decreased progressively since the age of five and he began to suffer from bilateral hearing loss after fever at the age of seven. Anti-infectious and immunoregulatory treatment was ineffective at that time. Physical examination showed that bilateral visual acuity decreased. Transient horizontal gaze-evoked nystagmus and bilateral hearing loss were detected. Obvious shaking was observed with closed eyes and toes together. Finger-to-nose, finger tracking, heel-knee-tibia and alternate motion tests were slightly inaccurate. Deep tendon reflexes disappeared and no pes cavus was observed. Pure tone audiometry revealed bilateral sensorineural hearing loss. Cranial magnetic resonance imaging indicated bilateral optic atrophy. ATP1A3 gene detection in the patient showed c. 2452G>A (p. Glu818Lys) heterozygous mutation while his parents were detected no such mutation in the same locus. Conclusions As for young patients who suffer from acute cerebellar ataxia after fever, disappeared tendon reflexes, atrophy of optic nerves or sensorineural hearing loss, they should be alerted to CAPOS syndrome when immunomodulating or anti-inflammatory therapy has been proved to be useless. Positive family history and ATP1A3 gene mutation would be beneficial to definite diagnosis.