Pharmacology · Year 2 · from Pharmacology
Case 2: ACE Inhibitor-Induced Angioedema
Clinical Scenario
A 58-year-old African American male presents with acute swelling of his lips and tongue 6 months after starting lisinopril.
Patient Demographics
- Age: 58 years
- Sex: Male
- Ethnicity: African American
- Weight: 95 kg
Chief Complaint
Progressive lip and tongue swelling for 3 hours
History of Present Illness
The patient started lisinopril 10 mg daily 6 months ago for hypertension. He has tolerated the medication well without cough. This morning, he woke up with mild lip swelling that has progressively worsened over 3 hours. He now has difficulty speaking due to tongue swelling and is beginning to feel "tightness" in his throat.
Physical Examination
- Vital Signs: BP 142/88 mmHg, HR 92 bpm, RR 20, T 37.0C, SpO2 97% on RA
- General: Anxious, muffled voice, drooling
- HEENT:
- Marked edema of upper and lower lips
- Tongue swelling extending to base
- Uvula edema visible
- No urticaria or rash
- Respiratory: Inspiratory stridor, no wheezing
- Cardiovascular: Tachycardic, regular
- Skin: No hives, no erythema
Workup and Results
| Test | Result | Reference Range |
|---|---|---|
| C4 complement | 22 mg/dL | 15-45 mg/dL |
| Tryptase | 5 ng/mL | <11 ng/mL |
| IgE | 45 IU/mL | <100 IU/mL |
| CBC | Normal | - |
Laryngoscopy: Significant edema of base of tongue and supraglottic structures
Diagnosis
ACE inhibitor-induced angioedema (bradykinin-mediated, not IgE-mediated)
Cardiovascular Pharmacology Principles Illustrated
- Bradykinin mechanism: ACE degrades bradykinin; ACE inhibition leads to bradykinin accumulation.
- Delayed onset: Can occur years after starting ACE inhibitor (unlike allergic reactions).
- Not histamine-mediated: Antihistamines and epinephrine are less effective; normal tryptase and IgE.
- Racial predisposition: African Americans have 3-5x higher risk due to differences in bradykinin metabolism.
- ACE inhibitor cough: Same mechanism (bradykinin accumulation in airways).
Treatment
- Airway management: Prepare for emergent airway; anesthesia and ENT backup
- Discontinue ACE inhibitor permanently
- Epinephrine 0.3-0.5 mg IM: May provide some benefit
- Fresh frozen plasma: Contains ACE and kininase II to degrade bradykinin
- Icatibant (bradykinin B2 receptor antagonist): If available, highly effective
- C1 esterase inhibitor concentrate: May help in severe cases
- Observation: Minimum 24-48 hours due to biphasic progression
- Alternative antihypertensive: ARBs are usually safe but carry small cross-reactivity risk
Clinical Image
ECG tracing demonstrating wide QRS complex tachycardia pattern. While this image shows a different arrhythmia, it demonstrates ECG changes that can occur with cardiovascular drug toxicity and interactions.
Image Source: Wikimedia Commons License: Public Domain URL: https://commons.wikimedia.org/wiki/File:Wide_complex_tachycardia.svg