C4A and hereditary angioedema: This case underscores the critical importance of differentiating between AAE and hereditary angioedema at initial presentation, as the management and prognosis differ. In patients presenting with angioedema, initial immunology workup should include C1-INH level, C1-INH function, C4, C1q, and Anti-C1 INH antibody levels to differentiate between hereditary and acquired forms of angioedema [7].