Nancy Klimas

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Nancy G. Klimas, MD, is an American researcher and physician who is the Director at the Institute for Neuro Immune Medicine at Nova Southeastern University in Miami and Ft. Lauderdale, Florida. She is, also: Director of Clinical Immunology Research, Miami VAMC; Professor of Medicine, Department of Clinical Immunology, College of Osteopathic Medicine, Nova Southeastern University; Chair, Department of Clinical Immunology, College of Osteopathic Medicine, Nova Southeastern University; and Professor Emerita, University of Miami, School of Medicine.[1]


  • 2014, Rudy Perpich Senior Lectureship Award, presented to a distinguished CFS/FMS scientist, physician or healthcare worker awarded by IACFS/ME[2]
  • 2011, Nelson Gantz Outstanding Clinician Award awarded to a physician who emulates Nelson Gantz's clinical acumen, his passion for medicine, and his empathy for persons with CFS/FM awarded by IACFS/ME[3]

2015 Institute of Medicine report[edit]

Dr. Klimas was one of the ME/CFS experts on the "Committee on the Diagnostic Criteria for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome" that was convened to produce the 2015 Institute of Medicine report.[4]

Case definition authorships[edit]

Klimas is one of the authors of the 2011 case definition, International Consensus Criteria,[5] as well as, one of the authors of the 2003 Canadian Consensus Criteria for ME/CFS, published as Myalgic Encephalomyelitis/Chronic Fatigue Syndrome:Clinical Working Case Definition,Diagnostic and Treatment Protocols[6]

Chronic Fatigue Syndrome Advisory Committee[edit]

Dr. Klimas served as a voting member of the Chronic Fatigue Syndrome Advisory Committee for the U.S. Department of Health and Human Services from April 1, 2007 to April 1, 2011.[7]

International Association for Chronic Fatigue Syndrome/Myalgic Encephalomyelitis[edit]

Dr. Klimas served as past President of the Board of Directors of the International Association for Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (IACFS/ME) from 2004-2009.[8] She has been awarded the IACFS/ME Nelson Gantz Outstanding Clinician Award (in 2011) and the IACFS/ME Rudy Perpich Senior Lectureship Award (in 2014).[9]

Notable studies[edit]

  • 2017, Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Gulf War Illness patients exhibit increased humoral responses to the Herpesviruses-encoded dUTPase: Implications in disease pathophysiology: Herpesviruses in ME/CFS and Gulf War Illness
    Abstract - Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and Gulf War Illness (GWI) are debilitating diseases with overlapping symptomology and there are currently no validated tests for definitive diagnosis of either syndrome. While there is evidence supporting the premise that some herpesviruses may act as possible triggers of ME/CFS, the involvement of herpesviruses in the pathophysiology of GWI has not been studied in spite of a higher prevalence of ME/CFS in these patients. We have previously demonstrated that the deoxyuridine triphosphate nucleotidohydrolases (dUTPase) encoded by Epstein-Barr virus (EBV), human herpesvirus-6 (HHV-6), and varicella-zoster virus (VZV) possess novel functions in innate and adaptive immunity. The results of this study demonstrate that a significant percentage of patients with ME/CFS (30.91-52.7%) and GWI (29.34%) are simultaneously producing antibodies against multiple human herpesviruses-encoded dUTPases and/or the human dUTPase when compared to controls (17.21%). GWI patients exhibited significantly higher levels of antibodies to the HHV-6 and human dUTPases than controls (p = 0.0053 and p = 0.0036, respectively), while the ME/CFS cohort had higher anti-EBV-dUTPase antibodies than in both GWI patients (p = 0.0008) and controls (p < 0.0001) as well as significantly higher anti-human dUTPase antibodies than in controls (p = 0.0241). These results suggest that screening of patients' sera for the presence of various combinations of anti-dUTPase antibodies could be used as potential biomarkers to help identify/distinguish patients with these syndromes and better direct treatment.[10]
  • 2017, Fecal metagenomic profiles in subgroups of patients with myalgic encephalomyelitis/chronic fatigue syndrome (FULL TEXT)
    Abstract - Background: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is characterized by unexplained persistent fatigue, commonly accompanied by cognitive dysfunction, sleeping disturbances, orthostatic intolerance, fever, lymphadenopathy, and irritable bowel syndrome (IBS). The extent to which the gastrointestinal microbiome and peripheral inflammation are associated with ME/CFS remains unclear. We pursued rigorous clinical characterization, fecal bacterial metagenomics, and plasma immune molecule analyses in 50 ME/CFS patients and 50 healthy controls frequency-matched for age, sex, race/ethnicity, geographic site, and season of sampling. Results: Topological analysis revealed associations between IBS co-morbidity, body mass index, fecal bacterial composition, and bacterial metabolic pathways but not plasma immune molecules. IBS co-morbidity was the strongest driving factor in the separation of topological networks based on bacterial profiles and metabolic pathways. Predictive selection models based on bacterial profiles supported findings from topological analyses indicating that ME/CFS subgroups, defined by IBS status, could be distinguished from control subjects with high predictive accuracy. Bacterial taxa predictive of ME/CFS patients with IBS were distinct from taxa associated with ME/CFS patients without IBS. Increased abundance of unclassified Alistipes and decreased Faecalibacterium emerged as the top biomarkers of ME/CFS with IBS; while increased unclassified Bacteroides abundance and decreased Bacteroides vulgatus were the top biomarkers of ME/CFS without IBS. Despite findings of differences in bacterial taxa and metabolic pathways defining ME/CFS subgroups, decreased metabolic pathways associated with unsaturated fatty acid biosynthesis and increased atrazine degradation pathways were independent of IBS co-morbidity. Increased vitamin B6 biosynthesis/salvage and pyrimidine ribonucleoside degradation were the top metabolic pathways in ME/CFS without IBS as well as in the total ME/CFS cohort. In ME/CFS subgroups, symptom severity measures including pain, fatigue, and reduced motivation were correlated with the abundance of distinct bacterial taxa and metabolic pathways. Conclusions: Independent of IBS, ME/CFS is associated with dysbiosis and distinct bacterial metabolic disturbances that may influence disease severity. However, our findings indicate that dysbiotic features that are uniquely ME/CFS-associated may be masked by disturbances arising from the high prevalence of IBS co-morbidity in ME/CFS. These insights may enable more accurate diagnosis and lead to insights that inform the development of specific therapeutic strategies in ME/CFS subgroups.[11]
  • 2017, Multi-Site Clinical Assessment of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (MCAM): Design and Implementation of a Prospective/Retrospective Rolling Cohort Study
    Abstract - In the Multi-Site Clinical Assessment of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (MCAM), we relied on expert clinician diagnoses to enroll patients from 7 specialty clinics in the United States in order to perform a systematic collection of data on measures of myalgic encephalomyelitis (ME)/chronic fatigue syndrome (CFS). Healthy persons and those with other illnesses that share some features with ME/CFS were enrolled in comparison groups. The major objectives were to: 1) use standardized questionnaires to measure illness domains of ME/CFS and to evaluate patient heterogeneity overall and between clinics; 2) describe the course of illness, identify the measures that best correlate with meaningful clinical differences, and assess the performances of questionnaires as patient/person-reported outcome measures; 3) describe prescribed medications, orders for laboratory and other tests, and management tools used by expert clinicians to care for persons with ME/CFS; 4) collect biospecimens for future hypothesis testing and for evaluation of morning cortisol profiles; and 5) identify measures that best distinguish persons with ME/CFS from those in the comparison groups and detect subgroups of persons with ME/CFS who may have different underlying causes. Enrollment began in 2012 and is planned to continue in multiple stages through 2017. We present the MCAM methods in detail, along with an initial description of the 471 patients with ME/CFS who were enrolled in stage 1."[12]
  • 2017, Telephone-administered versus live group cognitive behavioral stress management for adults with CFS
    Abstract - Objective: Chronic fatigue syndrome (CFS) symptoms have been shown to be exacerbated by stress and ameliorated by group-based psychosocial interventions such as cognitive behavioral stress management (CBSM). Still, patients may have difficulty attending face-to-face groups. This study compared the effects of a telephone-delivered (T-CBSM) vs a live (L-CBSM) group on perceived stress and symptomology in adults with CFS. Methods: Intervention data from 100 patients with CFS (mean age 50years; 90% female) participating in T-CBSM (N=56) or L-CBSM (N=44) in previously conducted randomized clinical trials were obtained. Perceived Stress Scale (PSS) and the Centers for Disease Control and Prevention symptom checklist scores were compared with repeated measures analyses of variance in adjusted and unadjusted analyses. Results: Participants across groups showed no differences in most demographic and illness variables at study entry and had similar session attendance. Both conditions showed significant reductions in PSS scores, with L-CBSM showing a large effect (partial ε2=0.16) and T-CBSM a medium effect (partial ε2=0.095). For CFS symptom frequency and severity scores, L-CBSM reported large effect size improvements (partial ε2=0.19-0.23), while T-CBSM showed no significant changes over time. Conclusions: Two different formats for delivering group-based CBSM-live and telephone-showed reductions in perceived stress among patients with CFS. However, only the live format was associated with physical symptom improvements, with specific effects on post-exertional malaise, chills, fever, and restful sleep. The added value of the live group format is discussed, along with implications for future technology-facilitated group interventions in this population.[13]
  • 2016, Poor sleep quality is associated with greater circulating pro-inflammatory cytokines and severity and frequency of chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) symptoms in women
    Abstract: Objective - Poor sleep quality has been linked to inflammatory processes and worse disease outcomes in the context of many chronic illnesses, but less is known in conditions such as chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME). This study examines the relationships between sleep quality, pro-inflammatory cytokines, and CFS/ME symptoms. Methods - Sixty women diagnosed with CFS/ME were assessed using the Pittsburgh Sleep Quality Index (PSQI), Fatigue Symptom Inventory (FSI) and Center for Disease Control and Prevention (CDC)-based CFS/ME symptom questionnaires. Circulating plasma pro-inflammatory cytokine levels were measured by ELISA. Multiple regression analyses examined associations between sleep, cytokines and symptoms, controlling for age, education, and body mass index. Results - Poor sleep quality (PSQI global score) was associated with greater pro-inflammatory cytokine levels: interleukin-1β (IL-1β) (β = 0.258, p = 0.043), IL-6 (β = 0.281, p = 0.033), and tumor necrosis factor-alpha (TNF-α) (β = 0.263, p = 0.044). Worse sleep quality related to greater fatigue severity (β = 0.395, p = 0.003) and fatigue-related interference with daily activities (β = 0.464, p < 0.001), and more severe and frequent CDC-defined core CFS/ME symptoms (β = 0.499, p < 0.001, and β = 0.556, p < 0.001, respectively). Conclusions - Results underscore the importance of managing sleep-related difficulties in this patient population. Further research is needed to identify the etiology of sleep disruptions in CFS/ME and mechanistic factors linking sleep quality to symptom severity and inflammatory processes."[14]
  • 2016, Illness progression in chronic fatigue syndrome: a shifting immune baseline[15]
  • 2016, Tracking post-infectious fatigue in clinic using routine Lab tests.
    Abstract: Background: While biomarkers for chronic fatigue syndrome (CFS) are beginning to emerge they typically require a highly specialized clinical laboratory. We hypothesized that subsets of commonly measured laboratory markers used in combination could support the diagnosis of post-infectious CFS (PI-CFS) in adolescents following infectious mononucleosis (IM) and help determine who might develop persistence of symptoms. Methods: Routine clinical laboratory markers were collected prospectively in 301 mono-spot positive adolescents, 4 % of whom developed CFS (n = 13). At 6, 12, and 24 months post-diagnosis with IM, 59 standard tests were performed including metabolic profiling, liver enzyme panel, hormone profiles, complete blood count (CBC), differential white blood count (WBC), salivary cortisol, and urinalysis....Results: Lower ACTH levels at 6 months post-IM diagnosis were highly predictive of CFS (AUC p = 0.02). ACTH levels in CFS overlapped with healthy controls at 12 months, but again showed a trend towards a deficiency at 24 months. Conversely, estradiol levels depart significantly from normal at 12 months only to recover at 24 months (AUC p = 0.02). Finally, relative neutrophil count showed a significant departure from normal at 24 months in CFS (AUC p = 0.01). Expression of these markers evolved differently over time between groups. Conclusions: Preliminary results suggest that serial assessment of stress and sex hormones as well as the relative proportion of innate immune cells measured using standard clinical laboratory tests may support the diagnosis of PI-CFS in adolescents with IM.[16]
  • 2016, Dr. Nancy Klimas, Dr. Irma Rey and several other researchers studied patients who developed gastroparesis following a viral history of flu-like symptoms or gastroenteritis. Nine at of the eleven patients with Idiopathic Gastroparesis studied (82 %) had active enterovirus infection on gastric biopsies. The study conclusion was that "antiviral and/or immune therapies against enterovirus seem to be favorable, as most of our patients had resolution of their gastroparesis symptoms after treatment. This is the first study to identify enterovirus as a possible infectious etiology of idiopathic gastroparesis.[17]

Earlier studies[edit]

Interviews & talks[edit]

There are many videos on YouTube of Nancy Klimas speaking about her work.[18]


  • "They experience a level of disability equal to that of patients with late-stage AIDS and patients undergoing chemotherapy"[20]

Open Letter to The Lancet[edit]

Two open letters to the editor of The Lancet urged the editor to commission a fully independent review of the PACE trial, which the journal had published in 2011. In 2016, Dr. Klimas, along with 41 colleagues in the ME/CFS field, signed the second letter.

Online presence[edit]

Learn more[edit]

See also[edit]


  5. Carruthers, BM; van de Sande, MI; De Meirleir, KL; Klimas, NG; Broderick, G; Mitchell, T; Staines, D; Powles, A C P; Speight, N; Vallings, R; Bateman, L; Baumgarten-Austrheim, B; Bell, DS; Carlo-Stella, N; Chia, J; Darragh, A; Jo, D; Lewis, D; Light, A; Marshall-Gradisnik, S; Mena, I; Mikovits, JA; Miwa, K; Murovska, M; Pall, ML; Stevens, S (2011), "Myalgic encephalomyelitis: International Consensus Criteria.", Journal of Internal Medicine, 270 (4): 327-38, PMID 21777306, doi:10.1111/j.1365-2796.2011.02428.x 
  10. Halpin, P; Williams, MV; Klimas, NG; Fletcher, MA; Barnes, Zachary; Ariza, ME (2017), "Myalgic encephalomyelitis/chronic fatigue syndrome and gulf war illness patients exhibit increased humoral responses to the herpesviruses-encoded dUTPase: Implications in disease pathophysiology", Journal of Medical Virology, PMID 28303641, doi:10.1002/jmv.24810 
  11. Nagy-Szakal, Dorottya; Williams, Brent L.; Mishra, Nischay; Che, Xiaoyu; Lee, Bohyun; Bateman, Lucinda; Klimas, Nancy G.; Komaroff, Anthony L.; Levine, Susan; Montoya, Jose G.; Peterson, Daniel L.; Ramanan, Devi; Jain, Komal; Eddy, Meredith L.; Hornig, Mady; Lipkin, W. Ian (2017), "Fecal metagenomic profiles in subgroups of patients with myalgic encephalomyelitis/chronic fatigue syndrome", Microbiome, 5 (44), doi:10.1186/s40168-017-0261-y 
  12. Unger, Elizabeth R.; Lin, Jin-Mann S.; Tian, Hao; Natelson, Benjamin H; Lange, Gudrun; Vu, Diana; Blate, Michelle; Klimas, Nancy G.; Balbin, Elizabeth G.; Bateman, Lucinda; Allen, Ali; Lapp, Charles W.; Springs, Wendy; Kogelnik, Andreas M.; Phan, Catrina C.; Danver, Joan; Podell, Richard N.; Fitzpatrick, Trisha; Peterson, Daniel L.; Gottschalk, C. Gunnar; Rajeevan, Mangalathu S.; MCAM Study Group (2017), "Multi-Site Clinical Assessment of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (MCAM): Design and Implementation of a Prospective/Retrospective Rolling Cohort Study.", American Journal of Epidemiology, 1–10, doi:10.1093/aje/kwx029 
  13. Hall, DL; Lattie, EG; Milrad, SF; Czaja, S; Fletcher, MA; Klimas, N; Perdomo, D; Antoni, MH (2017), "Telephone-administered versus live group cognitive behavioral stress management for adults with CFS", J Psychosom Res, 93: 41-47, doi:10.1016/j.jpsychores.2016.12.004 
  14. Milrad, Sara F.; Hall, Daniel L.; Jutagir, Devika R.; Lattie, Emily G.; Ironson, Gail H.; Wohlgemuth, William; Vera Nunez, Maria; Garcia, Lina; Czaja, Sara J.; Perdomo, Dolores M.; Fletcher, Mary Ann; Klimas, Nancy; Antoni, Michael H. (2016), "Poor sleep quality is associated with greater circulating pro-inflammatory cytokines and severity and frequency of chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) symptoms in women", Journal of Neuroimmunology, 0 (0), doi:10.1016/j.jneuroim.2016.12.008 
  15. Russell, Lindsey; Broderick, Gordon; Taylor, Renee; Fernandes, Henrique; Harvey, Jeanna; Barnes, Zachary; Smylie, AnneLiese; Collado, Fanny; Balbin, Elizabeth; Katz, Ben; Klimas, Nancy; Fletcher, Mary Ann (2016), "Illness progression in chronic fatigue syndrome: a shifting immune baseline", BMC Immunology, doi:10.1186/s12865-016-0142-3 
  16. Harvey, Jeanna M; Broderick, Gordon; Bowie, Alanna; Barnes, Zachary M; Katz, Ben Z; O'Gorman, Maurice R; Vernon, Suzanne D; Fletcher, Mary Ann; Klimas, Nancy; Taylor, Renee (2016), "Tracking post-infectious fatigue in clinic using routine Lab tests.", BMC Pediatrics, 16 (54), doi:10.1186/s12887-016-0596-8 
  17. Barkin, JA; Czul, F; Barkin, JS; Klimas, NG; Rey, IR; Moshiree, B (2016), "Gastric Enterovirus Infection: A Possible Causative Etiology of Gastroparesis", Digestive Diseases and Sciences, 61 (8): 2344-50, PMID 27344315, doi:10.1007/s10620-016-4227-x 
  18. YouTube - nancy klimas
  20. University of Miami ME/CFS Researcher Nancy Klimas, MD, Explains Complexity of Chronic Fatigue Syndrome in Terms That Anybody Can Understand

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From MEpedia, a crowd-sourced encyclopedia of ME and CFS science and history