C1 esterase inhibitor deficiency vs Terminal and central complement deficiencies
How to tell C1 esterase inhibitor deficiency and Terminal and central complement deficiencies apart when a board question makes them look alike.
C1-INH deficiency is bradykinin angioedema without hives; complement deficiencies present as recurrent Neisseria, pyogenic, or autoimmune-pattern infections.
Side by side
C1 esterase inhibitor deficiency causes hereditary angioedema with recurrent nonpruritic swelling, abdominal pain, low C4, and no urticaria.
C5-9 deficiency causes recurrent Neisseria infections; C3 deficiency causes severe recurrent pyogenic infections and immune-complex disease.
Low C1 esterase inhibitor increases kallikrein-bradykinin signaling, causing recurrent nonpruritic angioedema without urticaria; ACE-inhibitor angioedema is an acquired bradykinin mimic.
C5-9 deficiency causes recurrent Neisseria infections; C3 deficiency causes severe recurrent pyogenic infections and immune-complex disease.
The trap
C1 esterase deficiency is bradykinin angioedema; C5-9 is Neisseria; C3 is broad pyogenic and immune-complex susceptibility.
The repair move
Before naming the answer, force the stem through the separator: C1 esterase deficiency is bradykinin angioedema; C5-9 is Neisseria; C3 is broad pyogenic and immune-complex susceptibility.
Try a free question
CoreA 22-year-old woman has recurrent episodes of non-pruritic facial and lip swelling, hand swelling, and abdominal cramping lasting 2-3 days. There is no urticaria during these episodes. She does not improve with antihistamines or epinephrine. Family history reveals her mother had similar attacks. Serum C4 is low; C1 esterase inhibitor function is reduced. Which condition is most likely?
Show answer and explanation
Answer: A. Hereditary angioedema. Hereditary angioedema is autosomal dominant C1 esterase inhibitor deficiency (type I quantitative or type II functional). Without C1-INH, kallikrein-bradykinin pathway is unopposed; bradykinin causes recurrent non-pruritic angioedema (face, extremities, GI tract, larynx) WITHOUT urticaria. Antihistamines and epinephrine do NOT work. Treatment: C1-INH concentrate, ecallantide (kallikrein inhibitor), or icatibant (bradykinin receptor antagonist) acutely; danazol or C1-INH for prophylaxis.
Why the other choices are tempting
- B. Allergic anaphylaxis is IgE-mediated with urticaria and responds to epinephrine; this patient lacks urticaria and does not respond.
- C. ACE inhibitor angioedema is similar bradykinin mechanism but is acquired from ACE inhibitor use, not familial with low C4 and low C1-INH.
- D. Mastocytosis has elevated tryptase, urticaria pigmentosa, and mast cell infiltration, not the bradykinin angioedema pattern.
- E. Drug-induced urticaria has urticaria as a primary feature, not angioedema without urticaria.
Flashcards
Tap a card to flip it.
What clue supports C1 esterase inhibitor deficiency?
Choose C1 esterase inhibitor deficiency when the stem gives this pattern: C1 esterase inhibitor deficiency causes hereditary angioedema with recurrent nonpruritic swelling, abdominal pain, low C4, and no urticaria.
What clue supports Terminal and central complement deficiencies?
Choose Terminal and central complement deficiencies when the stem gives this contrasting pattern: C5-9 deficiency causes recurrent Neisseria infections; C3 deficiency causes severe recurrent pyogenic infections and immune-complex disease.
Quick answers
What is the fastest way to tell C1 esterase inhibitor deficiency from Terminal and central complement deficiencies?
C1-INH deficiency is bradykinin angioedema without hives; complement deficiencies present as recurrent Neisseria, pyogenic, or autoimmune-pattern infections.
What is the key clue for C1 esterase inhibitor deficiency?
C1 esterase inhibitor deficiency causes hereditary angioedema with recurrent nonpruritic swelling, abdominal pain, low C4, and no urticaria.
What is the key clue for Terminal and central complement deficiencies?
C5-9 deficiency causes recurrent Neisseria infections; C3 deficiency causes severe recurrent pyogenic infections and immune-complex disease.
What is the common trap with C1 esterase inhibitor deficiency vs Terminal and central complement deficiencies?
C1 esterase deficiency is bradykinin angioedema; C5-9 is Neisseria; C3 is broad pyogenic and immune-complex susceptibility.