Chronic fatigue syndrome: identification of distinct subgroups on the basis of allergy and psychologic variables.

BACKGROUND: We investigated a role for allergic inflammation and psychologic parameters in the development of chronic fatigue syndrome (CFS).
METHODS: The design was a comparison between subjects with CFS and age- and sex-matched control cohorts. Studies were performed on CFS subjects (n = 18) and control cohorts consisting of normal subjects (n = 11), allergic subjects (n = 14), and individuals with primary depression (n = 12). We quantified cytokines at baseline as cell-associated immunoreactive peptides and as transcripts evaluated by means of semiquantitative RNA-based polymerase chain reactions. Psychologic evaluations included administration of the Diagnostic Interview Schedule, the Structured Clinical Interview, and the Symptom Checklist 90-Revised.
RESULTS: Increases in tumor necrosis factor (TNF)-alpha were identified in individual subjects with CFS (50.1 +/- 14.4 pg TNF-alpha per 10(7) peripheral blood mononuclear cells [PBMCs]; mean +/- SEM) and allergic subjects (41.6 +/- 7.6) in comparison with normal subjects (13.1 +/- 8.8) (P < .01 and P < .05, respectively). Similar trends were observed for interferon (IFN)-alpha in allergic subjects (3.0 +/- 1.7 pg/10(7) PBMCs) and subjects with CFS (6.4 +/- 3.4) compared with normal subjects (1.9 +/- 1.4). A significant increase (P < .05) in TNF-alpha transcripts was demonstrated between subjects with CFS and depressed subjects. In contrast to these proinflammatory cytokines, both subjects with CFS (2.6 +/- 1.8 pg/10(7) PBMCs) and allergic subjects (3.4 +/- 2.8) were associated with a statistically significant (P < .01) decrease in IL-10 concentrations compared with normal subjects (60.2 +/- 18.2). As shown in other studies, most of our subjects with CFS were allergic (15 of 18) and therefore presumably demonstrated cytokine gene activation on that basis. The seasonal exacerbation of allergy was associated with a further increase in cellular IFN-alpha (from 2.1 +/- 1.2 to 14.2 +/- 4.5 pg/107 PBMCs; P < .05) but no further modulation of TNF-alpha or IL-10. Similarly, self-reported exacerbations of CFS were associated with a further increase in IFN-alpha (from 2.5 +/- 1.0 to 21.9 +/- 7.8; P < .05) and occurred at times of seasonal exposures to allergens. This linkage does not permit making any definitive conclusions regarding a causative influence of either seasonal allergies or the increase in cellular IFN-alpha with the increase in CFS symptoms. The close association between atopy and CFS led us to speculate that CFS may arise from an abnormal psychologic response to the disordered expression of these proinflammatory and antiinflammatory cytokines. Psychologic variables were predictive of immune status within the CFS sample (65.9% of the variance in immune status; F (3,10) = 6.44, P < .05). Specifically, the absence of a personality disorder but greater endorsement of global psychiatric symptoms was predictive of immune activation.
CONCLUSIONS: Most of our subjects with CFS were allergic, and the CFS and allergy cohorts were similar in terms of their immune status. However, the CFS subjects could be discriminated by the distinct psychologic profiles among subjects with and without immune activation. We propose that in at least a large subgroup of subjects with CFS who had allergies, the concomitant influences of immune activation brought on by allergic inflammation in an individual with the appropriate psychologic profile may interact to produce the symptoms of CFS. In a psychologically predisposed individual, symptoms associated with allergic inflammation are recognized as illness.