This is a syndrome that may or may not follow what appears to be an acute infectious illness, and may occur in epidemic or sporadic forms consisting of persisting or relapsing ‘fatigue’ or easy fatiguability of at least six months’ duration, for which no other cause is apparent. It is associated with a number of other variable features including mild fever, sore throat, painful lymph nodes, headaches, muscle pain, migratory arthralgia, photophobia, forgetfulness, irritability, concentration difficulties, depression, and sleep disturbance. It has been recognised since the early 1930s and known by a wide variety of names including Iceland disease, Royal Free disease, epidemic neuromyasthenia, myalgic encephalomyelitis, postviral syndrome, and more recently chronic fatigue syndrome.( 1 )
Although predominantly a disorder of young adults, it has been recognised in children with either an acute or insidious onset. At least 10-15 cases of the sporadic form are seen each year at the Hospital for Sick Children, Great Ormond Street, with lethargy, headache, abdominal pain, and subjective muscular weakness being the most common manifestations. Abnormal physical findings are usually conspicuous by their absence but occasionally pharyngeal injection, tender cervical lymph nodes, and muscle tenderness are present. A proportion of patients have an ‘atypical’ lymphocytosis, increased plasma creatine phosphokinase activity, circulating immune complexes, minor changes on electroencephalography and electromyelography, increased serum Epstein-Barr and Coxsackie B antibody titres, and VPI antigen in serum. Some workers have demonstrated enteroviral RNA in muscle biopsy material.(2 )Although an infective aetiology has been invoked, however, the full nature of the illness remains obscure and is probably a mixture of an initial infective insult followed by or associated with an important psychological component.
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Source: Lask B, Dillon MJ. Postviral fatigue syndrome. Arch Dis Child. 1990 Nov;65(11):1198. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1792622/