The Immunocompromised Child
Week 6: Immune System | Difficulty: Intermediate | Time: 40 minutes
Learning Objectives
- Apply knowledge of innate and adaptive immunity to clinical scenarios
- Explain the function of different white blood cell types
- Understand how chemotherapy affects immune function
- Describe the inflammatory response in immunocompromised patients
- Identify signs of infection in neutropenic patients
Case Presentation
Patient: Emma Thompson, 6-year-old female
Diagnosis: Acute Lymphoblastic Leukemia (ALL)
Treatment: Day 14 of induction chemotherapy
Chief Complaint: Fever for 8 hours, fatigue
Diagnosis: Acute Lymphoblastic Leukemia (ALL)
Treatment: Day 14 of induction chemotherapy
Chief Complaint: Fever for 8 hours, fatigue
Emma was diagnosed with ALL 2 weeks ago and is receiving induction chemotherapy. She presents today with fever and general malaise. Her mother reports she has been less active than usual and complained of chills. No cough, no urinary symptoms, no rash. She is currently neutropenic from chemotherapy.
Vital Signs & Examination
Temperature
38.8
°C
Heart Rate
128
bpm
Respiratory Rate
28
/min
Blood Pressure
95/58
mmHg
Physical Exam: Pale, tired-appearing child. No obvious source of infection identified. No pharyngitis, no otitis, clear lungs. Abdomen soft. No skin breakdown. Central line site clean.
Laboratory Results
| Test | Result | Normal Range |
|---|---|---|
| WBC | 0.8 x10⁹/L | 5.0-14.5 x10⁹/L |
| Absolute Neutrophil Count (ANC) | 0.2 x10⁹/L | >1.5 x10⁹/L |
| Hemoglobin | 78 g/L | 115-135 g/L |
| Platelets | 45 x10⁹/L | 150-400 x10⁹/L |
| C-Reactive Protein (CRP) | 85 mg/L | < 10 mg/L |
Clinical Reasoning Questions
1. Why is Emma at high risk for severe infection despite having no obvious source?
Correct! Severe neutropenia prevents normal immune response
Emma's ANC of 0.2 x10⁹/L represents profound neutropenia (ANC < 0.5 is severe). Neutrophils are the primary first-line defense against bacterial and fungal infections (innate immunity). Without adequate neutrophils, bacteria can proliferate unchecked without producing typical signs of infection (redness, swelling, pus). Fever may be the ONLY sign. This is called "febrile neutropenia" and is a medical emergency.
Emma's ANC of 0.2 x10⁹/L represents profound neutropenia (ANC < 0.5 is severe). Neutrophils are the primary first-line defense against bacterial and fungal infections (innate immunity). Without adequate neutrophils, bacteria can proliferate unchecked without producing typical signs of infection (redness, swelling, pus). Fever may be the ONLY sign. This is called "febrile neutropenia" and is a medical emergency.
2. Which type of immune cells are most affected by Emma's chemotherapy?
Correct! All rapidly dividing cells
Chemotherapy agents target rapidly dividing cells. This includes:
• Cancer cells (intended target)
• Bone marrow stem cells (unintended) → affecting production of all blood cells
• Hair follicles, GI mucosa (other rapidly dividing tissues)
The bone marrow suppression affects erythrocytes (anemia), leukocytes (neutropenia), and platelets (thrombocytopenia) - the "pancytopenia" seen in Emma's labs.
Chemotherapy agents target rapidly dividing cells. This includes:
• Cancer cells (intended target)
• Bone marrow stem cells (unintended) → affecting production of all blood cells
• Hair follicles, GI mucosa (other rapidly dividing tissues)
The bone marrow suppression affects erythrocytes (anemia), leukocytes (neutropenia), and platelets (thrombocytopenia) - the "pancytopenia" seen in Emma's labs.
3. Why might Emma not show typical signs of inflammation (redness, warmth, swelling) at an infection site?
Correct! Without neutrophils, inflammatory cascade cannot produce signs
Classic signs of inflammation (calor, rubor, dolor, tumor - heat, redness, pain, swelling) result from the inflammatory response mediated by neutrophils and other immune cells. Neutrophils release cytokines, histamine, and other mediators that cause vasodilation (redness, heat) and increased vascular permeability (swelling). Without neutrophils, these signs are absent or minimal even with severe infection. This makes diagnosis challenging in neutropenic patients.
Classic signs of inflammation (calor, rubor, dolor, tumor - heat, redness, pain, swelling) result from the inflammatory response mediated by neutrophils and other immune cells. Neutrophils release cytokines, histamine, and other mediators that cause vasodilation (redness, heat) and increased vascular permeability (swelling). Without neutrophils, these signs are absent or minimal even with severe infection. This makes diagnosis challenging in neutropenic patients.
Bioscience Integration
Innate vs Adaptive Immunity in Emma
Innate Immunity (Compromised):
- Neutrophils: ANC 0.2 - severely depleted. Primary defense against bacteria.
- Macrophages: Reduced in number and function
- Physical barriers: Mucosal damage from chemotherapy
Adaptive Immunity (Partially Compromised):
- B cells: Reduced antibody production
- T cells: Affected by chemotherapy, impaired cellular immunity
Emma is vulnerable to both typical and opportunistic pathogens.
Nursing Implications
- Immediate: Broad-spectrum antibiotics within 60 minutes of fever
- Protective isolation: Reverse barrier nursing to prevent introduction of pathogens
- Monitoring: Vital signs, temperature trends, any new symptoms (pain, GI changes)
- Supportive care: Growth factors (G-CSF) to stimulate neutrophil production
- Education: Family teaching about infection prevention at home