COMPLEMENT DEFICIENCY IN TWO PATIENTS WITH ABSENCE OF T-CELL RECEPTOR EXCISION CIRCLES ON NEWBORN SCREENING

Abstract

Introduction Most states use T-Cell Receptor Excision Circle (TREC) assays in routine newborn screening to identify infants with T cell defects. Some of these low TREC infants have normal T cell counts and function, without evidence of clinically significant disease. However, some of these low TREC infants without evidence of T cell dysfunction may develop serious infections, necessitating further immune evaluation. Case Description We present two infants whose initial newborn screens were flagged for low TREC numbers but had normal T cell number and function on further evaluation. These infants had significant infectious history – Patient 1 was an ex-36 week gestational age female who had necrotizing enterocolitis and intraabdominal abscess requiring resection, while Patient 2 was a term female who had streptococcal bacteremia leading to shock soon after birth, E. Coli tracheitis and recurrent ear infections in the first year of life. Further evaluation demonstrated complement deficiecy, in both – Patient 1 had low Mannose Bending lectin, while Patient 2 had low AH50 and properidin. Discussion These infants highlight the importance of using clinical history to guide the medical testing for all patients. Although both infants had low TRECs on their newborn screens, this could have been related to stress from their initial illness. The low TREC referral facilitated timely evaluation by clinical immunologists, even though their ultimate immunodefiency was in another arm of the immune system. An unintended consequence of routine TREC newborn screening may be earlier identification of primary immunodeficiency patients with non-T cell defects. Most states use T-Cell Receptor Excision Circle (TREC) assays in routine newborn screening to identify infants with T cell defects. Some of these low TREC infants have normal T cell counts and function, without evidence of clinically significant disease. However, some of these low TREC infants without evidence of T cell dysfunction may develop serious infections, necessitating further immune evaluation. We present two infants whose initial newborn screens were flagged for low TREC numbers but had normal T cell number and function on further evaluation. These infants had significant infectious history – Patient 1 was an ex-36 week gestational age female who had necrotizing enterocolitis and intraabdominal abscess requiring resection, while Patient 2 was a term female who had streptococcal bacteremia leading to shock soon after birth, E. Coli tracheitis and recurrent ear infections in the first year of life. Further evaluation demonstrated complement deficiecy, in both – Patient 1 had low Mannose Bending lectin, while Patient 2 had low AH50 and properidin. These infants highlight the importance of using clinical history to guide the medical testing for all patients. Although both infants had low TRECs on their newborn screens, this could have been related to stress from their initial illness. The low TREC referral facilitated timely evaluation by clinical immunologists, even though their ultimate immunodefiency was in another arm of the immune system. An unintended consequence of routine TREC newborn screening may be earlier identification of primary immunodeficiency patients with non-T cell defects.