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Di George Syndrome

Question:

6/16/2017
I am following a now 16 month old boy with 22q11 deletion with history of lymphopenia with total CD3 taken 6 months ago less than 2000 cells but otherwise normal T cell functional studies to mitogens and antigens. He has low IgA but normal G and M and normal antibody responses to IMZ. He also was dx with polyarticular arthritis and Rheum wanted to start Enbrel. Clinically he is doing well without significant infections and Rheum scheduled PPD skin testing (considering his age I wonder if it is reliable). If that's negative should I be concerned about any other contraindications for him to get Enbrel considering his low T cell counts? How reliable is a negative PPD on a 16 months old? Should I be ordering any other immune testing before Enbrel?


 
Answer:

Thank you for your question. We have ask Dr Notarangelo to provide input.

From Luigi D. Notarangelo, M.D.
Most patients with partial DiGeorge syndrome (as this one) do not have severe T cell dysfunction, and in fact may receive immunization with live vaccines. Unless this child received BCG immunization at birth (for some reason) or was exposed to TB, the PPD would be negative, and this would not tell us anything about T cell function. More reliable assays to measure T cell function are in vitro proliferation to mitogens (PHA) and to antigens (tetanus toxoid, candida) to which the infant has likely been exposed. Again, the vast majority of patients with DiGeorge syndrome do NOT have severe T cell dysfunction, and these tests may help confirm this. The polyarticular arthritis may be a sign of immune dysregulation which is not unusual in DiGeorge syndrome

Davies et al., J Rheumatol 2001; Keenan et al., Am J Med Genet 1997; Pelokonen et al., J Rheumatol 2002; Cron and Sullivan, J Pediatr 2006.

I hope this has been helpful.

Andrew Murphy, MD FAAAAI