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IM26.1-35 | Infectious Diseases — PBL Case

CLINICAL SETTING

Dr Kavitha is the registrar on call in the general medicine ward of a government medical college in Hyderabad during the post-monsoon season (October). She is teaching a final-year MBBS student, Arjun, who has just joined the clinical posting. The ward has 18 patients; the past two weeks have seen a cluster of febrile admissions. The case that will occupy their evening: Mr Rajan, a 28-year-old sanitation worker who was admitted 36 hours ago with a 6-day history of fever, myalgia, and headache. The admitting intern wrote in the case sheet: 'Viral fever — likely dengue. Paracetamol and IV fluids.' Rajan was initially stable. Tonight, the duty nurse calls Dr Kavitha: 'Patient in Bed 7 is confused and not responding well. His fever spiked to 40.2°C and there is some oozing from the IV cannula site.' As they walk to the bedside, Arjun opens the admission note. Dr Kavitha says: 'Before I examine him, tell me — what are the three most dangerous diagnoses we cannot miss in a 28-year-old with 6 days of fever, confusion, and bleeding in Hyderabad in October?'

Trigger 1: Trigger 1 — The Bedside Reveals More Than the Admission Note

Dr Kavitha examines Rajan. Findings: Temperature 40.2°C, pulse 110/min, BP 96/70 mmHg (pulse pressure 26 mmHg), SpO2 97% on room air, RR 22/min. He is confused (GCS 13/15: E3V4M6). Skin exam: petechiae over both lower limbs that were NOT documented in the admission note 36 hours ago. Abdomen: liver 3 cm below costal margin, spleen just palpable. No neck stiffness. Fundus: normal. The admission CBC (36 hours ago): platelets 85,000/microL, WBC 3600/microL, haematocrit 42%. A STAT CBC is drawn: platelets now 38,000/microL, haematocrit 48% (a 14% rise in 36 hours). Dengue NS1 antigen (from admission) is positive. Dr Kavitha turns to Arjun: 'Look at that haematocrit. Look at the pulse pressure. What is happening to this patient right now, and what do we need to do in the NEXT 30 MINUTES?'

DISCUSSION POINTS

  • The haematocrit has risen from 42% to 48% in 36 hours — what does this represent in dengue pathophysiology, and at what percentage rise is plasma leakage considered significant by WHO criteria?
  • Calculate the pulse pressure (96/70 mmHg). At what value does pulse pressure indicate impending dengue shock, and how does this guide the rate of fluid administration?
  • The petechiae were present on admission but not documented. What systematic examination approach in infectious disease patients would have detected them, and why does the skin exam matter in febrile illness beyond rash identification?
Click to reveal Trigger 2: Trigger 2 — Fluid Management Dilemma and a Second Diagnosis Emerges (discuss previous trigger first!)

Trigger 2: Trigger 2 — Fluid Management Dilemma and a Second Diagnosis Emerges

Arjun starts isotonic crystalloid (Ringer's lactate) at 5-7 mL/kg/hour as per the dengue protocol. Within 90 minutes, Rajan's BP improves to 108/74 mmHg, pulse 96/min. Dr Kavitha rechecks: pulse pressure is now 34 mmHg. The haematocrit on the repeat CBC at 2 hours is 44% (down from 48%) — appropriate response. However, reviewing the history more carefully, Arjun notices Rajan's occupation: sanitation worker who regularly unblocks drains and works in waterlogged sewage pits. His wife mentions he had bilateral conjunctival redness and mild jaundice three days ago, which they attributed to 'eye infection.' The current labs return: total bilirubin 3.4 mg/dL, ALT 210 IU/L, creatinine 2.1 mg/dL (baseline unknown), urine shows proteinuria and red cell casts. Dr Kavitha says: 'Dengue NS1 is positive, but look at these findings. Can dengue explain all of this? What other diagnosis must we now seriously consider, and how do we investigate it tonight?'

DISCUSSION POINTS

  • Can dengue explain the full clinical picture: conjunctival suffusion, jaundice, acute kidney injury (creatinine 2.1), and proteinuria with red cell casts? What additional diagnosis must be considered and what is the key epidemiological exposure that supports it?
  • What investigation would you order TONIGHT to evaluate for the second diagnosis, and at what stage of illness are IgM antibodies expected to become positive? What is the gold standard confirmatory test?
  • This patient may have DUAL infection. What is the clinical and therapeutic significance of co-infection with two or more vector-borne or water-borne pathogens — does treatment for one cover the other?
Click to reveal Trigger 3: Trigger 3 — Laboratory Results Force a Decision (discuss previous trigger first!)

Trigger 3: Trigger 3 — Laboratory Results Force a Decision

The following morning, Leptospira IgM ELISA returns POSITIVE. Blood cultures are pending (Day 2). The haematocrit has stabilised at 43%. Rajan's creatinine has risen to 2.8 mg/dL (Weil's disease pattern — hepatorenal syndrome). He remains mildly confused (GCS 14/15). The intensivist recommends nephrology input. Dr Kavitha must now make a treatment decision: she has dengue with early shock (recovered with fluids) AND leptospirosis with Weil's disease. The medical student Arjun asks: 'For dengue, we use supportive care — fluids and monitoring. But for leptospirosis, we need antibiotics. Which antibiotic do we give, at what dose, and what do we watch for in a patient whose kidneys are already compromised?' Meanwhile, the hospital infection control nurse appears: 'We have had 3 other febrile patients this week from the same ward who worked in the same area of the city. Should we report this cluster?'

DISCUSSION POINTS

  • What is the antibiotic of choice for severe leptospirosis (Weil's disease), at what dose and duration? Does renal impairment (creatinine 2.8 mg/dL) require dose adjustment for this antibiotic?
  • Dengue has no specific antiviral treatment — but what are the TWO most dangerous errors in fluid management during the dengue recovery phase (reabsorption phase on days 7-10) that can cause iatrogenic harm?
  • This appears to be a cluster of cases with a common occupational exposure. What public health actions are required: (a) notification obligations under the Integrated Disease Surveillance Programme (IDSP); (b) what environmental control measures should be recommended for the source area?
Click to reveal Trigger 4: Trigger 4 — Recovery, Reflection, and a New Patient at the Door (discuss previous trigger first!)

Trigger 4: Trigger 4 — Recovery, Reflection, and a New Patient at the Door

Rajan is discharged on Day 10 with improving renal function (creatinine 1.4 mg/dL, trending down). Before discharge, Dr Kavitha invites Arjun to conduct a structured discharge counselling session. Arjun attempts the counselling, but Rajan interrupts: 'Doctor, I have to go back to work. My family has no other income. I cannot afford to not unblock drains. How do I protect myself?' At this moment, a new patient arrives — a 22-year-old student returning from a trek in the Anamalai Hills, Tamil Nadu, with 5 days of fever, headache, and a single small necrotic lesion on the inner thigh. CBC: platelets 64,000, WBC 3200. Arjun notes the eschar and says: 'This is not dengue. This is something else entirely.' Dr Kavitha nods: 'You have 2 minutes to give me the diagnosis, the ONE diagnostic test, and the treatment.'

DISCUSSION POINTS

  • Rajan has occupational exposure that cannot be eliminated — what are the evidence-based personal protective measures and chemoprophylaxis option for leptospirosis that are applicable to a sanitation worker in India?
  • The new patient has a necrotic eschar on the inner thigh after a forest trek. What is the diagnosis, the single most useful diagnostic test tonight, and the treatment of choice? What would constitute a therapeutic diagnostic test?
  • Compare the approach to the acutely ill febrile patient in three settings: (a) post-monsoon Hyderabad urban sanitation worker; (b) forest-trekker returned from Anamalai Hills; (c) hostel student with non-blanching rash. How does the epidemiological context change the diagnostic priority list before any laboratory results are available?

Group Task Assignments

  • Construct a dengue fluid management protocol for a ward nurse that covers: (a) when to start IV fluids, at what rate, and using which fluid type; (b) the haematocrit and pulse pressure thresholds that trigger escalation in rate; (c) when to STOP or slow fluids (the reabsorption phase danger). Present as a one-page algorithmic flowchart with decision nodes.
  • Design a 'Syndromic Fever Chart' for use at the bedside of any newly admitted febrile patient that captures: the epidemiological exposure history (occupation, travel, vector exposure, animal contact, water contact), the five examination findings most likely to distinguish the cause (eschar, rash character, organomegaly, conjunctival signs, lymphadenopathy), and the three first-line investigations tailored to the local season/geography.
  • Draft the discharge counselling summary for Rajan (or a patient in a similar situation) — in simple language (Class 8-10 reading level equivalent), covering: diagnosis in accessible terms, why the full antibiotic course must be completed, three specific personal protection steps for his occupation, and when to return to hospital (warning signs).
  • Debate: 'In post-monsoon India, all febrile patients with thrombocytopaenia should receive doxycycline empirically to cover rickettsia, even before scrub typhus is confirmed.' Identify arguments for and against this position, considering stewardship, diagnostic accuracy, and clinical risk of missing scrub typhus.

Learning Issues

Research these questions and bring your findings to the discussion.

  1. [IM26.25] What are the WHO dengue clinical stages (without warning signs, with warning signs, severe dengue), the haematocrit and pulse pressure thresholds for each, and the fluid management protocol for dengue with warning signs?
  2. [IM26.18] What are the clinical features that distinguish Weil's disease (severe leptospirosis) from uncomplicated leptospirosis, and what is the treatment for severe leptospirosis including dose adjustments in renal impairment?
  3. [IM26.20] What are the clinical features, diagnostic approach, and treatment of scrub typhus, including the sites to examine for the eschar and why the Weil-Felix OX-K test is used as a bedside surrogate?
  4. [IM26.7] How does the epidemiological exposure history change the differential diagnosis and investigation priority in the acutely ill febrile patient — specifically comparing urban water-borne, forest/vector-borne, and institutional outbreaks?
  5. [IM26.34] How do you structure a discharge counselling session for a patient who has had a notifiable infectious disease, covering diagnosis communication, treatment completion, and specific occupational prevention measures?
  6. [IM26.35] What personal protective measures and chemoprophylaxis options are available for leptospirosis in occupationally exposed workers, and under what circumstances is doxycycline post-exposure prophylaxis recommended in India?