🧵 When It’s Not Sepsis – Clues That It’s Actually Autoimmunity

Fever.
Tachycardia.
High CRP.
Looks like sepsis—but cultures stay negative, and antibiotics don’t work.

Let’s break down how to catch autoimmune mimicry of infection—before it’s too late. 👇
@IhabFathiSulima @DrIanWeissman @DrAkhilX @CelestinoGutirr @NeuroSjogrens @SarahSchaferMD @drkeithsiau #MedTwitter #RheumTwitter

1. The classic setup:

Patient has:
✅ Fever
✅ High CRP
✅ High neutrophils
✅ Looks toxic

But…
🧪 Cultures are negative
🧫  Antibiotics fail
🧠 Something’s not adding up 

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2. When you should pause:

🚩 No response to antibiotics after 48–72 hrs
🚩 Blood cultures negative
🚩 No source on imaging
🚩 Worsening cytopenias
🚩 Rising liver enzymes or ferritin
🚩 Mental status changes 

3. Common autoimmune mimics of infection

🔥 Adult-onset Still’s Disease (AOSD)
🔥 Macrophage Activation Syndrome (MAS)
🔥 Systemic Lupus Erythematosus (SLE)
🔥 Vasculitis
🔥 TMA / CAPS
🔥 Drug-induced fevers 

4. Ferritin is your friend

📈 In autoimmune mimics:
– CRP ↑
– PCT ↔ or mild ↑
– Ferritin = SKY HIGH (>3,000 to >10,000)

🧠 Ferritin >10,000? Think MAS, AOSD, HLH. 

5. Procalcitonin gives you a clue

🔥 High in bacterial infections
📉 Low/normal in MAS, SLE flares, vasculitis
⚠️ But not perfect—use in context 

6. Don’t forget the cytopenias

📉 Drop in Hb, WBC, or platelets with fever?
Could be:
– MAS/HLH
– Lupus
– TMA
– Bone marrow involvement 

7. Clotting with fever? That’s a scream.

Fever + thrombosis =
– APS
– CAPS
– TMA
– Malignancy
– Catastrophic flare 

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8. Don’t miss the window for steroids

When it’s MAS, CAPS, SLE crisis or vasculitis:
💊 Steroids can save lives
💉 Delay kills

If infection is ruled out (or covered), start early immunosuppression. 

📌 Takeaway

Not all fever is infection.
When cultures are silent and inflammation is loud—
Think autoimmune.
Think MAS, SLE, AOSD, vasculitis.
And act early.

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That “non-resolving sepsis” patient might need a rheumatologist, not more meropenem.