MP CFS ME

 A

A “severe, unremitting” chronic fatigue presentation should be approached as (1) urgent triage for alternative diagnoses/complications, (2) systematic exclusion of common and high-risk mimics, and (3) confirmation of ME/CFS features and severity to guide supportive management. There is no confirmatory biomarker; testing is used to identify alternative or comorbid explanations. (1)(2)

## 1) First visit: safety screen + phenotype the syndrome

### A. Confirm this is “chronic fatigue” and not a different primary symptom

- Time course: onset (post-infectious vs gradual), duration, variability, triggers, functional decline from baseline.

- Core ME/CFS phenotype: *post-exertional malaise (PEM)*, unrefreshing sleep, cognitive dysfunction ± orthostatic intolerance (OI). (Different criteria sets vary, but PEM is highly discriminating clinically.) (2)(3)

### B. Identify red flags that should divert away from an ME/CFS-first pathway

Examples (not exhaustive): fever/weight loss/night sweats, focal neurologic deficits, inflammatory arthritis/synovitis, GI bleeding, progressive cardiopulmonary symptoms, new severe headache/temporal symptoms, significant lymphadenopathy/splenomegaly, recurrent infections/immunodeficiency signs, high-risk substance use, medication/toxin exposure. (If present: expand workup urgently/appropriately.)

### C. Medication/substance and iatrogenic fatigue review (high yield)

Sedatives (benzodiazepines, Z-drugs), antihistamines, anticholinergics, opioids, gabapentinoids, beta-blockers, centrally acting antihypertensives, antipsychotics, some antidepressants, isotretinoin, interferons, alcohol/cannabis, supplements (e.g., excess melatonin). Consider polypharmacy and withdrawal states.

## 2) Targeted physical exam (include objective function and autonomic screening)

- Full exam with cardiopulmonary, abdominal, lymph nodes, joint exam for synovitis, skin (rash/photosensitivity), neuro exam.

- Orthostatic vitals (active stand preferred in clinic): supine HR/BP then at 1–3–5–10 minutes standing; evaluate for POTS/OH and symptom reproduction (lightheadedness, palpitations, “brain fog”). OI is common and changes management.

- Weight/BMI, hydration status, signs of malnutrition/deconditioning vs primary neuromuscular disease.

## 3) Baseline laboratory evaluation (rule-out panel), then branch by clues

CDC emphasizes tailoring tests to the presentation; the main goal is ruling out other illnesses. (1)

A pragmatic “minimum reasonable” baseline set many clinicians use:

- CBC with differential

- CMP (electrolytes, renal/hepatic function, calcium, albumin)

- TSH (± free T4 if abnormal or suspicion)

- ESR and/or CRP (inflammatory signal)

- Fasting glucose or HbA1c

- Ferritin + iron/TIBC (or at least ferritin), especially if menstruating, restless legs, or microcytosis

- Vitamin B12 and folate (CDC notes some clinicians include these, particularly with cognitive impairment) (1)

- Urinalysis (± urine protein/creatinine if indicated)

- Pregnancy test when relevant

Common “add-ons” based on prevalence/risk or symptom pattern:

- Vitamin D (commonly included in initial testing by ME/CFS-experienced clinicians) (1)

- Celiac serology (tTG-IgA + total IgA) if GI symptoms, iron deficiency, weight loss, or autoimmune background

- CK if prominent myalgias/weakness or concern for myopathy

- Morning cortisol *only if* clinical features suggest adrenal insufficiency (unexplained weight loss, hypotension, hyperpigmentation, hyponatremia, hyperkalemia), not as routine screening

- HIV, hepatitis B/C, TB testing, etc., based on risk assessment and exposure history

Autoimmune/rheumatologic tests (ANA, ENA, RF/anti-CCP, complements) should be *symptom-driven* (true inflammatory arthritis, rashes, sicca, Raynaud, serositis, neuropathy), rather than routine screening in isolated fatigue.

## 4) High-yield comorbidity/mimic evaluation (often missed in “unremitting” cases)

### A. Sleep disorders (very common; treatable)

- Screen: snoring, witnessed apneas, morning headaches, EDS, RLS/PLMD.

- Consider PSG/home sleep apnea testing when indicated (especially with obesity, resistant HTN, AF, loud snoring, EDS).

### B. Mood, anxiety, trauma-related disorders, and substance use

A mental status exam and depression assessment are recommended in chronic fatigue evaluations; depression commonly coexists and must be treated on its own merits. (3)

Clinical point: depression can mimic fatigue, but PEM (delayed symptom crash after exertion) is more typical of ME/CFS than primary depression.

### C. Orthostatic intolerance / dysautonomia

If orthostatic vitals suggest POTS/OH or symptoms strongly indicate OI:

- Consider ECG, volume status review, medication contributors

- Consider referral for tilt-table or autonomic testing if diagnostic uncertainty or severe disability.

### D. Post-infectious syndromes (including Long COVID/PASC)

Document triggering infection, timing, and evolution; consider directed evaluation for organ-specific sequelae when symptoms warrant (e.g., exertional desaturation, myocarditis symptoms, thromboembolic risk).

### E. Endocrine and metabolic conditions

Beyond thyroid: diabetes, adrenal insufficiency (as above), pituitary disease (history-driven), significant electrolyte disorders.

### F. Cardiopulmonary disease

If dyspnea, chest pain, syncope, edema, new exercise intolerance beyond PEM pattern:

- ECG, BNP/troponin when indicated, echocardiogram, chest imaging, spirometry, ambulatory rhythm monitoring—directed by symptoms/exam.

### G. Neurologic disease

If focal deficits, progressive weakness, true objective cognitive decline, seizures, abnormal neuro exam:

- Neuroimaging/EEG/LP as clinically indicated; consider MS, neuroinflammatory disease, myasthenia, etc.

### H. Malignancy and chronic infection (selective)

Pursue with constitutional symptoms, abnormal exam, cytopenias, markedly abnormal inflammatory markers, persistent focal pain, etc.

## 5) Diagnostic confirmation of ME/CFS (after exclusion) and severity stratification

- ME/CFS is a clinical diagnosis requiring characteristic symptoms and exclusion of alternative explanations. (2)

- NICE supports a comprehensive assessment, investigation to exclude other diagnoses, and then coordinated multidisciplinary care; it also provides severity framing (mild → very severe) and specific considerations for severe/very severe disease. (4)

For *severe/very severe* presentations, also explicitly assess:

- Nutrition/hydration adequacy, weight trajectory, swallowing/GI intolerance

- Pressure injury risk, venous thromboembolism risk (individualized), bone health risk (immobility, low intake)

- Caregiver support, safeguarding, and ability to access services/homebound care

- Sensory hypersensitivities that limit clinic testing and require accommodation

## 6) Practical workflow (how to sequence)

1. **Visit 1:** red flags + orthostatic vitals + medication review + baseline labs + depression/anxiety screen; schedule close follow-up.

2. **Visit 2:** review labs; if unrevealing and phenotype fits, document working diagnosis; address comorbid sleep/OI/pain/mood; add directed testing (sleep study, echo, autoimmune tests, etc.) only if indicated.

3. **Ongoing:** periodic re-evaluation—patients can later declare new diagnoses; CDC recommends periodic reassessment and continued routine preventive screening. (2)

## Clarifying details (so I can tailor the differential “branching”)

- Any **PEM** (delay, duration, reproducibility)? Any orthostatic symptoms?

- Unintentional weight loss, fevers/night sweats, focal neuro symptoms?

- Key meds/substances? Snoring/apnea symptoms?

- Post-infectious onset (EBV/COVID-like illness) vs gradual? Duration >6 months (or >3 months per NICE framework)? (4)