Table 1:

Non–SCID conditions that may lead to an abnormal T-cell receptor excision circle–based newborn screen for SCID^{10, 23, 31–36}

Non-SCID causes of T-cell lymphopenia	Examples
Syndromic disorders and congenital abnormalities	Trisomy 18
	Trisomy 21
	DiGeorge syndrome
	CHARGE syndrome
	Ataxia–Telangiectasia syndrome
Secondary T-cell lymphopenia	Cardiac or gastrointestinal anomalies
	Multiple congenital anomalies
	Neonatal leukemia
	T-cells losses into third space (e.g., hydrops or vascular leakage)
	Prenatal exposure to purine antagonists
Preterm birth
Idiopathic T-cell lymphopenia
Combined immunodeficiencies with dysfunctional T cells	DOCK8 deficiency
	Wiskott–Aldrich Syndrome

Note: SCID = severe combined immunodeficiency.