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Thursday, March 23, 2017

Treatment of infants identified as having severe combined immunodeficiency by means of newborn screening

Severe Combined Immunodeficiency (SCID) is a set of fatal immune disorders in which infants are born without proper functioning immune systems needed to fight off infections.  Fortunately, in recent years, there has been a push in several states for newborn screening (NBS) for early identification and life-saving treatment of these children.  In this month’s issue of JACI, Dorsey and colleagues describe the protocol that they use in California, which has successfully identified 32 SCID patients and 46 non-SCID patients with decreased levels of T-cells (J Allergy Clin Immunol 2017; 139(3): 733-742).

Newborn screening is performed by measuring TRECs (T-cell receptor excision circles) which are formed upon gene rearrangement of the T-cell receptor.  Peripheral blood count with differential and flow cytometry is the first follow up testing to determine the number of lymphocytes. This is followed by functional lymphocyte testing. If SCID is suspected, then children are placed in protective isolation and aggressively treated with antibiotics if needed.  A SCID social worker coordinates with family in order to manage workup and identify needs for support, including emotional support. 

 Because allogenic and autologous hematopoietic stem cell (HSC) transplant is life-saving, Dorsey and colleagues relay that they apply three principles: (1) use of a donor with the least likelihood of graft-versus-host disease (GVHD), (2) minimize the duration of waiting for the SCT, and (3) use the least amount of chemotherapy necessary.  Adherence to these principles has led to good outcomes: among the 32 that underwent transplant, 29 (94%) are alive and well. 

Among the non-SCID patients, the protocol is more reliant on the degree of immunodeficiency, but nevertheless, they are followed up very closely by immunologists in the coming years to identify the status of their immune dysfunction.  There remains a lot of work to be done in order to find out the best way to identify and treat SCID, but nationwide screening promises to accelerate our reaching that goal.

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