Abnormal TREC-Based Newborn Screening Test ina Premature Neonate with Massive Perivillous FibrinDeposition of the Placenta

Severe combined immunodeficiency (SCID), a primary immunodeficiency arising from variable defects in lymphocyte develop-ment and survival, is characterized by significant deficiency of thymus derived (T-) lymphocytes and variable defects in the B-lymphocyte population. Newborn screening for SCID is based on detection of low numbers of T-cell receptor excision circles(TRECs) by real time quantitative PCR (RT-qPCR). This screening allows for early identification of individuals with SCID andother disorders characterized by T-lymphopenia. Higher rates of abnormal screens are commonly seen in premature and criticallyill neonates, often representing false positives. It is possible that many abnormal screens seen in these populations are result ofconditions that are characterized by systemic inflammation or stress, possibly in the context of stress-induced thymic involution.We present a case of a male infant delivered at 27 weeks, 6 days of gestation, with severe intrauterine growth restriction whohad an abnormal TREC screen and amassive perivillous fibrin deposition(MPFD) of the placenta. This association has not beenreported previously. We are raising the awareness to the fact that conditions, such as MPFD, that can create adverse intrauterineenvironment are capable of causing severe stress-induced thymic involution of the fetus which can present with abnormal TRECresults on newborn screening