Abnormal Newborn SCID Screen and Lymphopenia in an Infant Exposed to in Utero Folfirinox Chemotherapy

Rationale: Newborn screening for severe combined immune deficiency measures T-cell receptor excision circles (TRECs) as a biomarker for naive T-cell production.  Other non-SCID conditions have been reported to cause a positive SCID newborn screens such as 22q deletion syndrome, CHARGE syndrome and idiopathic CD4 lymphopenia.  Here we report an infant girl who presented with initial absent TRECs and mild T-cell lymphopenia after in utero exposure to 7 cycles of 5-fluorouracil, irinotecan, and oxaliplatin (FOLFIRINOX) during the second and third trimester for maternal treatment of pancreatic cancer. 

Methods: TREC screen by Washington State Department of Health and flow cytometry by Seattle Children’s laboratory. 

Results: Patient's initial TREC screen was 14#/μL at 23 hours of life (critically low 0-20#/μL).  Flow cytometry at 3 days of life (dol) revealed T and NK cell lymphopenia with a CD3 count of 1035 but normal CD4CD45RA+ percentage (80%).  On dol 7 TRECs were still low at 8#/μL but CD3 count rose to 1303.  At dol 28, TRECs increased to 120 and the patient’s lymphopenia resolved with normal mitogen response to PHA.  We recommended the patient proceed with her normal infant vaccines with the exception of live viral vaccines.  

Conclusions: We believe this is the first reported case of an abnormal SCID newborn screen induced by in utero exposure to FOLFIRINOX chemotherapy.  It is reassuring that both TRECs and lymphopenia normalized with time.  The lag in TRECs recovery compared to the T-cell count may indicate a reversible thymic dysfunction related to the in utero chemotherapy exposure.