Phenotypes of chronic fatigue syndrome in children and young people

Objective To investigate the heterogeneity of chronic fatigue syndrome (CFS/ME) in children and young people. Setting Regional specialist CFS/ME service Patients Children and young people aged <19 years old. Methods Exploratory factor analysis was performed on symptoms present at assessment in 333 children and young people with CFS/ME. Linear and logistic regression analysis of data from self-completed assessment forms was used to explore the associations between the retained factors and sex, age, length of illness, depression, anxiety and markers of severity (fatigue, physical function, pain and school attendance). Results Three phenotypes were identified using factor analysis: muscoloskeletal (factor 1) had loadings on muscle and joint pain and hypersensitivity to touch, and was associated with worse fatigue (regression coefficient 0.47, 95% CI 0.25 to 0.68, p<0.001), physical function (regression coefficient -0.52, 95% CI -0.83 to -0.22, p=0.001) and pain. Factor 2 (migraine) loaded on noise and light hypersensitivity, headaches, nausea, abdominal pain and dizziness and was most strongly associated with physical function and pain. Sore throat phenotype (factor 3) had loadings on sore throat and tender lymph nodes and was not associated with fatigue or pain. There was no evidence that phenotypes were associated with age, length of illness or symptoms of depression (regression coefficient for association of depression with musculoskeletal pain -0.02, 95% CI -0.27 to 0.23, p=0.87). The migraine phenotype was associated with anxiety (0.40, 95% CI 0.06 to 0.74, p=0.02). Implications CFS/ME is heterogeneous in children with three phenotypes at presentation that are differentially associated with severity and are unlikely to be due to age or length of illness.