Examkin

Question

Difficulty: Very hardPediatric Infectious Diseases

A 14-month-old boy is brought to the emergency department due to a 4-day history of high fever, severe respiratory distress, and a progressively worsening rash. His medical history is significant for a conotruncal cardiac anomaly (truncus arteriosus) that was surgically repaired at 1 week of age. His neonatal intensive care course was complicated by recurrent generalized tonic-clonic seizures that resolved after intravenous calcium gluconate infusions. He has had no recent sick contacts and does not attend daycare. Three weeks ago, he received his routine 12-month childhood immunizations at a mobile health clinic.

On physical examination, his temperature is 39.5°C (103.1°F), heart rate is 175/min, and respiratory rate is 55/min. Oxygen saturation is 86% on room air. The patient appears lethargic and toxic. Skin examination reveals a diffuse eruption of umbilicated vesicles on an erythematous base covering his face, trunk, and extremities. Several of the vesicles are hemorrhagic. Chest auscultation reveals diffuse bilateral crackles.

Laboratory evaluation shows:
Leukocyte count: 3,200/mm³
Neutrophils: 80%
Lymphocytes: 15%
Monocytes: 5%
Serum calcium: 8.2 mg/dL (normal: 8.5–10.5 mg/dL)

Chest radiograph demonstrates diffuse, bilateral nodular interstitial infiltrates.

Which of the following is the most appropriate next step in targeted pharmacotherapy for this patient?

  1. Intravenous acyclovirAnswer
  2. B
    Intravenous vancomycin and cefepime
  3. C
    Intravenous immune globulin and high-dose aspirin
  4. D
    Intramuscular epinephrine and intravenous methylprednisolone
  5. E
    Nebulized albuterol and intravenous dexamethasone

Answer

Intravenous acyclovir is the correct targeted pharmacotherapy for this patient's disseminated vaccine-strain varicella infection.
The correct answer is intravenous acyclovir. This patient's presentation is highly suspicious for a severe, disseminated vaccine-strain Varicella-Zoster Virus (VZV) infection resulting from the inappropriate administration of a live-attenuated vaccine to a severely immunocompromised host. The patient's history of truncus arteriosus (a conotruncal cardiac defect) and neonatal hypocalcemia (causing seizures) is classic for DiGeorge syndrome (22q11.2 deletion). This syndrome involves aberrant development of the third and fourth pharyngeal pouches, leading to absent or hypoplastic parathyroid glands and thymus. Thymic aplasia results in a profound T-cell deficiency, evidenced by this patient's severe lymphopenia (absolute lymphocyte count of 480/mm³). Live-attenuated vaccines, such as MMR and varicella, are strictly contraindicated in individuals with severe cellular immunodeficiency. The patient received his 12-month immunizations 3 weeks ago, and now presents with a diffuse, umbilicated, vesicular rash (some hemorrhagic) and nodular pneumonia, a classic description of disseminated varicella. Intravenous acyclovir is the antiviral drug of choice for severe or disseminated VZV infections, particularly in immunocompromised patients.

Step-by-Step Solution

1
Analyze the patient's past medical history.
The combination of truncus arteriosus (conotruncal anomaly) and neonatal hypocalcemia (recurrent seizures responsive to calcium) strongly suggests DiGeorge syndrome (22q11.2 deletion syndrome).
Identifying the underlying congenital syndrome is critical because it dictates the patient's immune status.
2
Evaluate the patient's immune status based on the syndrome.
DiGeorge syndrome is characterized by thymic aplasia or hypoplasia, which leads to severe T-cell immunodeficiency (confirmed by the patient's profound absolute lymphopenia of 480/mm³).
T-cell deficiency fundamentally alters how the patient handles infections and vaccines.
3
Correlate the immune status with the recent clinical intervention.
The patient received routine 12-month immunizations, which include the live-attenuated measles, mumps, and rubella (MMR) and varicella vaccines. Live-attenuated vaccines are absolutely contraindicated in patients with severe T-cell deficiency.
Administration of a live vaccine to an immunocompromised host can cause unrestricted viral replication and severe, disseminated vaccine-strain infection.
4
Diagnose the acute presentation based on clinical findings.
The patient presents with an umbilicated, vesicular, and hemorrhagic rash along with diffuse nodular infiltrates (pneumonia) exactly 3 weeks after vaccination. This is the classic presentation of severe, disseminated Varicella-Zoster Virus (VZV) infection.
Vesicles on an erythematous base are the hallmark of herpesvirus infections, specifically VZV in this context.
5
Determine the optimal targeted pharmacotherapy.
The appropriate treatment for disseminated VZV, particularly in an immunocompromised host, is prompt initiation of intravenous acyclovir.
Acyclovir inhibits viral DNA polymerase and is the antiviral of choice for severe VZV infections.

Key Concept

Patients with DiGeorge syndrome (22q11.2 deletion) frequently have profound T-cell immunodeficiency due to thymic aplasia; administration of live-attenuated vaccines (e.g., MMR, varicella) is absolutely contraindicated as it can lead to fatal disseminated vaccine-strain infections. Disseminated varicella requires urgent treatment with intravenous acyclovir.
Estimated Time:1m 30s
Rate this question

Topics

Pediatric Infectious Diseases

More questions from this topic