Enterovirus related metabolic myopathy: a postviral fatigue syndrome
- 1Division of Clinical Neurosciences and Psychological Medicine, Imperial College, London SW7, UK
- 2Biomedical Sciences, Imperial College
- Correspondence to: Dr R Lane West London Neurosciences Centre, Charing Cross Hospital, Fulham Palace Road, London W6 8RF, UK;
- Received 15 March 2002
- Accepted 8 May 2003
Objective: To detect and characterise enterovirus RNA in skeletal muscle from patients with chronic fatigue syndrome (CFS) and to compare efficiency of muscle energy metabolism in enterovirus positive and negative CFS patients.
Methods: Quadriceps muscle biopsy samples from 48 patients with CFS were processed to detect enterovirus RNA by two stage, reverse transcription, nested polymerase chain reaction (RT-NPCR), using enterovirus group specific primer sets. Direct nucleotide sequencing of PCR products was used to characterise the enterovirus. Controls were 29 subjects with normal muscles. On the day of biopsy, each CFS patient undertook a subanaerobic threshold exercise test (SATET). Venous plasma lactate was measured immediately before and after exercise, and 30 minutes after testing. An abnormal lactate response to exercise (SATET+) was defined as an exercise test in which plasma lactate exceeded the upper 99% confidence limits for normal sedentary controls at two or more time points.
Results: Muscle biopsy samples from 20.8% of the CFS patients were positive for enterovirus sequences by RT-NPCR, while all the 29 control samples were negative; 58.3% of the CFS patients had a SATET+ response. Nine of the 10 enterovirus positive cases were among the 28 SATET+ patients (32.1%), compared with only one (5%) of the 20 SATET− patients. PCR products were most closely related to coxsackie B virus.
Conclusions: There is an association between abnormal lactate response to exercise, reflecting impaired muscle energy metabolism, and the presence of enterovirus sequences in muscle in a proportion of CFS patients.
- chronic fatigue syndrome
- postviral fatigue syndrome
- enterovirus RNA sequences
- muscle energy metabolism
- CFS, chronic fatigue syndrome
- RT-NPCR, reverse transcription, nested polymerase chain reaction
- SATET, subanaerobic threshold exercise test
↵* Professor L Archard and Dr R Lane designed and coordinated the study. Dr Lane (West London Neurosciences Centre, Charing Cross Hospital) recruited and assessed the patients and performed or supervised the subanaerobic threshold exercise testing, needle muscle biopsies and other investigations. Professor Archard, B Soteriou, and H Zhang (Cell and Molecular Pathology Group of the Division of Biomedical Sciences, Imperial College Faculty of Medicine) carried out the molecular investigations including reverse transcription, nested polymerase chain reactions, nucleotide sequencing, and comparative sequence analysis on biopsy samples and control tissues.
Competing interests: none declared