<prompt> A patient presents with recurrent swelling of the lips as shown. He has no itching. Family history is positive. Which of the following is deficient in this patient?C1,C2,C4C1 inhibitorC3b inactivatorC5-C8  <response>: This boy presents with features of hereditary angioneurotic edema, which is due to deficiency of C1 inhibitor. C1 inhibitor deficiency - Hereditary angioedema. C1, C2, C4 deficiency - Collagen vascular disorders C5-C8 deficiency - Recurrent bacteremia with Neisseria. Reference: Ananthanarayan and Paniker;s Textbook of Microbiology Tenth edition 