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Clinical Workup: 26-Year-Old Male, Recurrent Fever After Discharge

Clinical Summary (What We Know)

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Step 1 - Think About the Top Differentials

A. Rickettsial Disease (Most Likely, Inadequately Treated)

• Subacute fever for weeks, tachycardia, hypoxia
• Bilateral consolidation / interstitial pneumonia (develops in severe cases due to vascular endothelial injury - Harrison's 22E, Section 192)
• Responds to doxycycline
• BUT: treatment duration matters - requires 7-15 days oral doxycycline; if discharged early on a short course, relapse is expected
• In severe scrub typhus, combination doxycycline + azithromycin is superior to monotherapy (Harrison's 22E); some strains (especially in South/Southeast Asia) are doxycycline-resistant and respond only to azithromycin + rifampin

B. HIV / Immunodeficiency with Opportunistic Infection

• 26-year-old male: HIV must be excluded first
• PJP (Pneumocystis jirovecii Pneumonia): bilateral diffuse infiltrates, severe hypoxia disproportionate to clinical appearance, responds to steroids acutely, relapses without adequate TMP-SMX treatment
• CMV pneumonitis, cryptococcal disease, atypical mycobacteria (MAC) - all possible in undiagnosed HIV
• The use of steroids without HIV testing/PJP treatment is potentially dangerous

C. Pulmonary Tuberculosis ± Co-infection

• 1-month fever, young male, bilateral consolidation in a TB-endemic region
• Sputum smear/GeneXpert may be negative early
• Steroid-induced immune suppression can unmask TB

D. Fungal Infection

• Pulmonary histoplasmosis, aspergillosis, or mucormycosis (especially if immunocompromised or diabetic)
• Can mimic bacterial pneumonia, respond partially to antibiotics, then relapse

E. Autoimmune / Cryptogenic

• Cryptogenic organizing pneumonia (COP): fever, patchy consolidation, good steroid response but classic relapse on steroid taper
• Hypersensitivity pneumonitis
• Eosinophilic pneumonia

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Step 2 - Workup on Re-presentation

Tier 1 - MUST DO Immediately

Tier 2 - High Yield if HIV Positive or Immunocompromised

Tier 3 - If Rickettsial Relapse Suspected

Tier 4 - If Autoimmune / COP Suspected

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Step 3 - Examine the Patient Again (Do Not Skip This)

• Eschar (painless black scab, often missed - axilla, groin, behind ear, hairline) - pathognomonic of scrub typhus
• Lymphadenopathy - scrub typhus, HIV, lymphoma
• Hepatosplenomegaly - rickettsial disease, HIV, lymphoma, TB
• Rash - maculopapular (rickettsial, measles); oral thrush (HIV/immunocompromise)
• Weight loss history - TB, HIV, malignancy
• Risk factors for HIV - sexual history, IV drug use, transfusion history

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Step 4 - Immediate Management While Awaiting Results

1. Do NOT restart steroids blindly - if PJP or TB is possible, steroids alone will worsen the patient
2. Continue/resume doxycycline (100 mg PO BD) if rickettsial relapse is suspected, but for a full 14-day total course with azithromycin combination if severe
3. If HIV+ with CD4 <200 and PJP suspected: Start TMP-SMX (15-20 mg/kg/day in 3-4 divided doses) + adjunctive prednisolone only if PaO2 <70 mmHg
4. Empirical TB treatment only if AFB positive or strong clinical suspicion confirmed by GeneXpert
5. Repeat SpO2 and blood gas to assess current respiratory status

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Diagnostic Algorithm Summary

Re-presented fever
       │
       ├── HIV test (MANDATORY FIRST)
       │        │
       │        ├── HIV+ → CD4, viral load, PJP workup, CrAg, CMV
       │        │
       │        └── HIV– → Continue below
       │
       ├── CBC: Leukopenia + thrombocytopenia? → Rickettsia/Scrub typhus serology
       │
       ├── Look for eschar → Scrub typhus PCR + serology
       │
       ├── Sputum AFB + GeneXpert → TB excluded?
       │
       ├── LDH markedly elevated → PJP even if HIV–? (consider BAL)
       │
       └── Steroid taper relapse + no infection found → COP → Lung biopsy

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Key Teaching Points in This Case

1. A 5-day prednisolone course after rickettsial disease may suppress fever temporarily but does not treat the underlying infection - relapse is predictable if doxycycline was not continued for a full course (7-15 days total)
2. Severe scrub typhus with pneumonitis benefits from combination doxycycline + azithromycin, not monotherapy, per a 2023 NEJM trial cited in Harrison's 22E
3. Bilateral patchy consolidation + severe hypoxia + young male = always exclude HIV/PJP before attributing to any other cause
4. Cryptogenic organizing pneumonia is a classic steroid-taper-relapse diagnosis - but only made after infections are excluded
5. Do not discharge a febrile patient with hypoxia on short steroid course without a confirmed diagnosis - this creates exactly the scenario seen here

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• Harrison's Principles of Internal Medicine 22E (2025), Chapter 192 "Rickettsial Diseases" - scrub typhus clinical features, diagnosis, and combination therapy recommendation
• Goldman-Cecil Medicine, Chapter on Pneumocystis jirovecii pneumonia
• Scrub typhus combination antibiotic therapy review (Chung et al., Infect Chemother, 2023 - PMID 37407239)
• Scrub typhus presenting as lobar pneumonia (Vihari et al., Natl Med J India, 2024 - PMID 39448532)