Snapshot A 15-year-old boy is rushed to the emergency department by his mother due to increased difficulty with breathing. His mother says that he does not have a food allergy and that this has happened to him before after undergoing a dental procedure. She reports that in the father's side of the family, they suffer from these episodes of swelling but usually self resolve. On physical exam, the patient has swelling of the lips, tongue, and skin around the face and arms. He is immediately sedated and subsequently intubated and treated for anaphylaxis which does not improve his symptoms. Laboratory testing is significant for decreased C4 and C1 inhibitor levels as well as normal C1q levels. Introduction Clinical definition hereditary C1 inhibitor deficiency that leads to recurrent angioedema without urticaria or pruritus triggers include login to view 8 more bullets Genetics inheritance pattern autosomal dominant Associated conditions possibly associated with an increased incidence of autoimmune disease Prognosis variable after the attack occurs, they may recur throughout the patient's life login to view 1 more bullet Epidemiology Incidence 0.001%-0.003% of the general population Demographics typically begins in childhood and worsens during puberty Location skin, upper airway, and gastrointestinal tract Risk factors family history ETIOLOGY Pathophysiology pathobiology C1 inhibitor deficiency (hereditary angioedema type I) or dysfunction (hereditary angioedema type II) results in login to view 4 more bullets Presentation Symptoms prodromal symptoms fatigue nausea and/or other gastrointestinal symptoms flu-like symptoms angioedema without urticaria or pruritus affecting the skin login to view 2 more bullets upper airway login to view 1 more bullet gastrointestinal login to view 2 more bullets Physical exam skin erythema marginatum may be seen upper airway voice changes or horseness stridor shortness of breath gastrointestinal abdominal tenderness ascites signs of small bowel obstruction Studies Labs ↓ C4 and C2 levels normal C1q levels C1 inhibitor levels low level (hereditary angioedema type I) normal level (hereditary angioedema type II) Differential Drug-induced anaphylaxis Contact dermatitis Atopic dermatitis Superior vena cava syndrome Treatment Conservative securing airway, breathing, and circulation indication login to view 3 more bullets Medical plasma-derived C1 inhibitor indication login to view 3 more bullets other medications that can be used in the acute treatment of hereditary angioedema includes login to view 3 more bullets attenuated androgens (e.g., danazol) indication login to view 1 more bullet Complications Asphyxiation can result in death ≥ 30% mortality in patients with laryngeal angioedema can present with decreased inspiratory and expiratory rate and should be treated promptly w/epinephrine (histaminergic angioedema)