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DR8.1-5 | Common Viral Infections — PBL Case

CLINICAL SETTING

It is Tuesday morning in the dermatology ward of a district general hospital in South India. Dr Priya, a final-year MBBS student on her 4-week dermatology clinical posting, is accompanying the senior registrar on the morning ward round. Three patients are to be reviewed. Dr Priya has been asked to lead the bedside presentation for each patient and to propose a management plan before the registrar comments. The ward nurse hands her three brief clerking notes as they enter the ward.

Trigger 1: Mr Rajan, 62 years, retired schoolteacher — Ward Bed 3

Clerking note: Mr Rajan was admitted 3 days ago with severe burning pain over the left side of his chest, initially attributed to musculoskeletal pain. Yesterday a band of grouped vesicles appeared on the left thorax extending from the spine to the anterior chest wall, stopping exactly at the midline. He is a known diabetic on metformin. He rates the pain 8/10. His wife is 6 months pregnant and has never had chickenpox. His CD4 count is normal. The ward nurse asks Dr Priya whether the pregnant wife who visited yesterday is at risk.

DISCUSSION POINTS

  • What is the clinical diagnosis and what two features of the rash pattern make it unambiguous? Why does this eruption stop at the midline?
  • What is the underlying virology — which virus, which phase of its lifecycle, and from which anatomical site does the reactivation originate?
  • Mr Rajan is diabetic and 62 years old. How do these factors influence (a) your antiviral choice and dosing schedule, and (b) the risk of a specific long-term complication you must discuss with him?
  • The ward nurse's question about the pregnant wife: what is the actual infectious risk, what disease would she develop (not Mr Rajan's disease), and what immediate action is indicated?
Click to reveal Trigger 2: Meena, 9 years, brought by her mother — Paediatric Side Room (discuss previous trigger first!)

Trigger 2: Meena, 9 years, brought by her mother — Paediatric Side Room

Clerking note: Meena was admitted yesterday evening with a 2-day fever followed by an intensely itchy rash that started on the trunk and is now on the face and scalp, with very few lesions on the arms and legs. On examination the rash shows macules, papules, clear vesicles, and crusted lesions all present at the same time. She is otherwise healthy and fully vaccinated except — her mother recalls — the varicella vaccine was not available at their local centre. Her 6-year-old brother at home has not been vaccinated. The mother asks if her daughter is still infectious and when she can return to school. She also mentions their elderly grandfather, who has never had chickenpox, came to visit yesterday.

DISCUSSION POINTS

  • Identify the two morphological features of this rash that clinch the diagnosis. Explain the biological mechanism that produces both features simultaneously.
  • Meena's rash is centripetal — what does this mean, and how does it differ from the distribution pattern of the other herpesvirus disease seen on this morning's ward round (Mr Rajan's condition)?
  • Meena is immunocompetent. What is the role (if any) of antiviral therapy in her case? How would your answer change if she were on long-term steroids for nephrotic syndrome?
  • Address the mother's two questions using accurate virology: (a) when does Meena cease to be infectious, and (b) what is the specific risk to the unvaccinated grandfather and what should be done within 96 hours?
Click to reveal Trigger 3: Arun, 19 years, engineering student — Outpatient Consultation Room (discuss previous trigger first!)

Trigger 3: Arun, 19 years, engineering student — Outpatient Consultation Room

Clerking note (outpatient, referred from GP): Arun presents with two complaints. First, he noticed 6 pearly, dome-shaped papules on his lower abdomen and one on the inner thigh over the past 3 weeks; each has a small central dimple; no pain or itch. He has been sexually active with two partners in the past 2 months. He is anxious and initially thought these were 'warts from HPV'. His second complaint: he has 8 rough, hyperkeratotic papules on the dorsum of both hands, present for 8 months, with interrupted skin markings and tiny dark dots visible on close inspection. He tried over-the-counter cream with no improvement.

DISCUSSION POINTS

  • Arun has two separate viral skin conditions. Identify each, name the causative virus (including virus family), and give the ONE morphological sign that distinguishes the abdominal/thigh lesions from the hand lesions.
  • Arun believes the abdominal lesions are caused by HPV. Clarify this misunderstanding: explain the correct causative agent, its virus family, and one fundamental difference in its cellular mechanism compared with HPV.
  • For the abdominal/thigh lesions, what is the correct STI classification in this context, what investigations (if any) should be requested, and what are the management options? Should Arun's partners be notified?
  • For the hand lesions: what is the first-line treatment, what is the mechanism of action of that treatment, and what is the prognosis given that he is immunocompetent? What bedside test distinguishes these lesions from a corn on the palm?
Click to reveal Trigger 4: Synthesis and Integration — End-of-Round Discussion (discuss previous trigger first!)

Trigger 4: Synthesis and Integration — End-of-Round Discussion

After the ward round, the registrar asks the students to sit together and prepare a one-page summary for the departmental teaching file. The registrar poses three integration questions before leaving.

DISCUSSION POINTS

  • Across all three patients, two different virus families are represented. List them, identify which patient had which family, and explain the single most important difference in their replication strategies (nuclear vs cytoplasmic; latency vs no-latency).
  • A Tzanck smear was requested for Mr Rajan and Meena. Both showed multinucleate giant cells. A medical student says 'So both have the same virus?' — correct this misunderstanding precisely, stating what the Tzanck smear does and does not tell you, and what test would definitively distinguish the two.
  • Design a one-page patient information leaflet (bullet points only) for a parent whose child has just been diagnosed with molluscum contagiosum — addressing: what causes it (virus family, one sentence), how it spreads, whether it is serious, when to seek medical attention, and whether the child can attend school.