C2 Deficiency Presenting as Pseudomonas Aeruginosa Bacteremia

Abstract

C2 deficiency (C2D) is the most common homozygous complement deficiency, leading to susceptibility to infection with encapsulated bacteria due to defective opsonization. Pseudomonas aeruginosa is not a typical encapsulated bacterium, although reports have indicated that it can activate the complement system. Here we present an infant with Pseudomonas aeruginosa bacteremia who subsequently was diagnosed with C2D. Immunoglobulins, CH50, C2 level and function and C4 level were performed by the National Jewish Health Complement Laboratory and ARUP Laboratories. A 10-month-old Hispanic male with no significant past medical history presented to the hospital with a 2 day history of vomiting, diarrhea and fever to 102oF. Because of his progressive illness, he was admitted to the hospital for infectious workup. His blood culture grew Pseudomonas aeruginosa after 24hrs while urine and CSF cultures were negative. He was treated with ceftazidime without any complications. An immunodeficiency evaluation revealed normal immunoglobulin levels and normal sweat chloride test. His CH50 = 0 (60-144), C4 = 12 mg/dL (16-47), C2 = 2.8 mcg/mL (22.2-39.8), and C2 function = 21084 Units/mL (15354-46242). C2 levels for his father and mother were 15.1 and 16.9, respectively. C2D can present with Pseudomonas aeruginosa bacteremia. One study has demonstrated that the serum of a patient with C2 defect showed weak bactericidal activity against Pseudomonas aeruginosa strains as compared to normal serum. This case illustrates the importance of C2 in protecting from non-encapsulated bacteria that can evade the complement system. Complement system should be evaluated in patients with Pseudomonas bacteremia.