Idiopathic T cell lymphopenia identified in New York State Newborn Screening

Abstract

Quantification of T-cell receptor excision circles (TRECs) for newborn screening for SCID has advanced the diagnosis of severe combined immune deficiency (SCID). However, it has led to the identification of infants with T cell lymphopenia without known cause. The clinical characteristics, appropriate laboratory monitoring, and outcomes of patients remain unclear. We performed a retrospective review of clinical and laboratory studies for 26 infants collected from 7 New York State referral centers from 2010 to 2016 with low TRECs (mean, 70copies/μl) and subnormal CD3 counts (mean, 1150/cubicmm). Over time absolute CD3 counts increased in 17 and decreased in 9; 22 (85%) have done well clinically regardless of absolute T cell values. Additional infants with TCL will continue to be identified in newborn screening panels. While most patients seem to do well clinically, parameters for diagnosis and monitoring have yet to be formalized, and additional information needs to be collected, causes and outcomes reported.

Keywords: Idiopathic T-cell lymphopenia; Newborn screening; Severe combined immunodeficiency; TREC level.

Fig. 1

Correlation between the initial TREC value and the absolute CD3 T cell number for the 26 infants.

Fig. 2

The first and more recent CD3T cell count for each infant. The normal CD3 T cell ranges 1,500 and 2,500 cu/mm used in newborn screening reports [9,11] are indicated with dotted lines. Dashed lines = two reference cut off values.

Fig. 3

Serial CD3 counts in 11 infants; the number shown indicates the patient from Tables 1 and 2. CD3 T cell normal ranges are 1,500 and 2,500 cu/mm [9,11].