Patient handout

Atypical Pneumonia (Mycoplasma / Chlamydophila / Legionella / psittacosis / Q fever)

PRODUCTION

1. Your condition

This handout is for atypical pneumonia (mycoplasma / chlamydophila / legionella / psittacosis / q fever). Your care team identified this based on: subacute dry cough, low-grade fever, headache, myalgia, sore throat — gradual onset (2025 ats cap; mp/c.pneumoniae pattern).

Other reasons your team may use this plan: extrapulmonary features — rash/mucositis or hemolysis or neurologic (mp ~25% extrapulmonary, lofgren pmid 34532621); gi/encephalopathy/relative bradycardia (legionella); patchy / interstitial infiltrate disproportionate to exam (2025 ats cap; pmid 40679934); urinary legionella antigen positive (serogroup-1 sens 0.86, spec ~1.00; kawasaki pmid 34972680).

2. Your medications

Take these medications exactly as prescribed. Do not stop or change a dose without talking to your provider.

Medication	Starting dose	How	When	What it does
doxycycline	100 mg PO BID (200 mg load if severe atypical concern)	PO	q12h × 5 d (afebrile-stable; longer if Legionella/psittacosis/Q fever)	2025 ATS CAP first-line atypical-active for low-resistance reliability — covers Mp incl. macrolide-resistant strains, C. pneumoniae, C. psittaci, Coxiella; preferred where MRMP prevalence high (Ding PMID 38634891). RxCUI 3640 RxNav-confirmed 2026-05-16.
azithromycin	500 mg PO ×1 then 250 mg PO daily ×4 d	PO	daily × 5 d total	2025 ATS CAP atypical-active; preferred in pregnancy and where local Mp macrolide resistance is low. Verify QTc + statin interaction. RxCUI 18631 RxNav-confirmed 2026-05-16.
clarithromycin	500 mg PO BID	PO	q12h × 5 d	Macrolide alternative; more drug interactions (CYP3A4) than azithromycin. RxCUI 21212 RxNav-confirmed 2026-05-16.
levofloxacin	750 mg PO daily	PO	daily × 5 d	Reserve respiratory FQ for intolerance / Legionella concern / significant comorbidity — covers typical + all atypicals (2025 ATS CAP). RxCUI 82122 RxNav-confirmed 2026-05-16.

Plan: 2025 ATS CAP — atypical-active empiric → pathogen-directed → resistance/failure ladder (severity × pregnancy × resistance-risk × comorbidity)

3. When to call your provider

Contact your care team if any of the following happen:

oxygen level (SpO₂) <92% on room air → ED
CURB-65 ≥2 → ED
Failure of oral therapy at 48-72 h → ED + resistance/alternate-dx workup
Hyponatremia + altered mentation + relative bradycardia suggesting severe Legionella → ED
Hemolysis (dark urine, jaundice) or extensive mucositis (MIRM) → ED (Lofgren PMID 34532621)

4. When to seek emergency care

Call 911 or go to the nearest emergency room right away if you have:

Urinary Legionella antigen positive — L. pneumophila serogroup-1 pooled sensitivity 0.86 (95% CI 0.78-0.91), specificity ~1.00 (0.99-1.00) → very high LR+, rules IN serogroup-1; a NEGATIVE result does NOT exclude non-sg1/non-pneumophila Legionella
Suspected/confirmed Legionella with respiratory failure / septic shock / multilobar disease / encephalopathy / acute renal failure / rhabdomyolysis (CPK ≥5× ULN)(life-threatening)
Mp + cold-agglutinin hemolytic anemia, MIRM (rash + mucositis), encephalitis/transverse myelitis, or myocarditis
No clinical/radiographic improvement at 48-72 h on an atypical-active regimen despite adequate coverage
Atypical-pattern pneumonia in transplant / biologic / HIV / chronic-steroid host

5. Follow-up

Public-health reporting for Legionella (notifiable; environmental source investigation if cluster) and psittacosis/Q fever (zoonotic notifiable); Q fever serology surveillance for chronic endocarditis in valvulopathy/immunocompromise; pneumococcal + influenza + COVID vaccination; smoking cessation; CXR follow-up at 6 wk if smoker / age ≥50

6. Sources

Guideline: 2025 ATS Diagnosis and Management of CAP — Official ATS Clinical Practice Guideline (Niederman, AJRCCM 2025;212(1):24; PMID 40679934; DOI 10.1164/rccm.202507-1692ST) + IDSA/CDC Legionellosis context; updates 2019 ATS/IDSA CAP (PMID 31573350)