Comorbidity of chronic fatigue syndrome, postural tachycardia syndrome, and narcolepsy with 5,10-methylenetetrahydrofolate reductase (MTHFR) mutation in an adolescent: a case report

A 16-year-old male adolescent was hospitalized complaining of intermittent dizziness,drowsiness,and fatigue for approximately 2 years.The patient had an episode of fever and pharyngalgia lasting nearly 2 weeks and had undergone appendectomy because of acute appendicitis before the presentation of the above symptoms.He suffered from severe dizziness mostly after switching from a supine to an upright posture when he was getting up in the morning.The symptom of dizziness usually persisted for minutes to hours and could be partially alleviated by recumbency.In addition,he felt drowsy and fatigued all day despite a total sleep duration of 14 to 15 h per day.All the symptoms could be partially mitigated by complete bed rest for 1 or 2 weeks,but he relapsed after taking part in normal school life again.Additionally,the feeling of fatigue was obviously aggravated after exertion or infection.He was unable to focus on his studies and had to withdraw from school for a long time.As a result,there was a decline in academic performance after the onset of illness.He used to benefit from taking carnitine and folate;however,the improvement was limited in enabling him to take part in normal social and school life.He was physically and mentally healthy before the presentation and did not feel disgusted with learning in the past.No family history of cardiovascular or nervous system disease was evident.The study was approved by the Ethics Committee of Peking University First Hospital(No.2020-415).