I have been referred two infants with congenital heart disease for evaluation following an abnormal TREC newborn screen. In both patients, reparative surgery was complicated by chylothorax and subsequent thoracic duct ligation. I feel confident that the abnormal newborn screens were related to the lymphocytopenia from the chylous effusion: both had a normal initial TREC screens (with screens 2 and 3 being abnormal following surgery), there was no lymphopenia prior to surgery; they have normal IgM levels, and good PHA mitogen responses. Within 2 weeks of surgery, CD3+ levels were 800-1500/uL and CD19+ were from 491-575/uL.

What I'm not sure about is how long to expect the lymphocytopenia to persist. Is there any utility in following T cell subset levels periodically, and if so, how often? Can live viral vaccines be given?


Thank you for your inquiry.

I am going to refer your inquiry to Dr. Jennifer Puck, who is an internationally recognized expert in TREC screening and immunodeficiency disorders. When we hear from Dr. Puck, we will forward her response to you.

Thank you again for your inquiry.

Phil Lieberman, M.D.

We received a response from Dr. Jennifer Puck. Thank you again for your inquiry and we hope this response is helpful to you.

Phil Lieberman, M.D.

Response from Dr. Jennifer Puck:
There are multiple reasons why this baby might have low TRECs and low T cells, and any and all of them might be contributing:

  • a congenital condition underlying the heart defect that ALSO causes delayed or impaired T cell development (some children who do not have 22q deletion have primary problems with T cells)
  • a secondary T lymphocytopenia due to 3rd spacing and chylous leakage from the vasculature
  • thymectomy incidental to cardiac surgery, known to cause decreased T cells.

Different states that screen newborns with TRECs define the abnormal cutoff as well as T lymphocytopenia differently (and other than the HIV literature there are not good data on how many T cells need to be present to avoid PCP or other opportunistic infections). In California we use 1500 T cells/uL as a cutoff. Unless there are other indications of immune problems, we do not continue to follow infants with T cells above this level and have allowed them to receive live attenuated rotavirus vaccine and other vaccines according to the standard schedules.

For babies such as you describe, I would agree with checking their PHA responses and Ig levels, and would continue to follow T cell numbers over time until they normalize. This may take a couple of months or a year or more, depending on what is causing the T cells to be low.

I have them get the primary series of killed vaccinations and then at 7 months (or a month after the last of the 2-4-6 month vaccines) check antibodies to tetanus and prevnar along with a repeat lymphocyte subset study. If the killed vaccine responses are good I allow live vaccines after the 1st birthday but by that time rotavirus vaccine is not given since it is for younger babies.

I also make sure babies like this get synagis during RSV season.

Hope this helps.
Jennifer Puck, MD

Close-up of pine tree branches in Winter Close-up of pine tree branches in Winter