A five year-old ex 36 weeker with hx of gastroschisis and six month NICU stay found to have lymphopenia on routine blood work by her pediatrician one year ago. Lymphocyte subset one year ago were CD3 (#350), CD4 (#182), CD8 (#108), normal B and NK cell. Follow up Lym subset in May 2019 were CD3 (#195), CD4(#86), CD8(#59), normal B and NK. Invitae PID panel showed no known genetic defect for PID.
T cell subsets at Mayo lab in 5/19: CD4CD45RA (46%, #38), CD4CD45RO (54%, #44), CD8CD45RA (91%, #53), CD8CD45RO (8%, #5). TREC study at Mayo lab in 6/19: CD3 (#244, 865-3618), CD4 (#121, 497-2267), CD8 (#79, 243-1303). CD4 RTE at Mayo lab in 6/19: CD4 absolute (#139, 582-1630), CD4 RTE % (25.7, 25.8-68), CD4 RTE absolute (#36, 170-1007). This result is consistent with decreased thymic output. Immunoglobulin levels showed normal IgG and IgA with low IgM. PHA study in 8/18 was low response but repeated PHA, ConA and PMW in 5/19 showed normal response. Clinically the patient has been well without having bacterial or opportunity infections, normal growth for height and weight. The patient received MMR vaccine at age of 4 without developing any reaction.
HIV study was negative. No chronic diseases. GI consult was normal. What is the next step for T-cell lymphopenia (likely thymic output problem so far) and management?