Newborn screening for severe combined immunodeficiency: an opportunity for intervention.

Severe combined immunodeficiency (SCID) is a potentially fatal disorder characterized by defective T- and B-lymphocyte function. We describe a 34-week female twin who had developed feeding intolerance, perioral cyanosis, abdominal distension and neutropenia at 1 month of age. Despite several evaluations including an 'inconclusive' newborn screening result for SCID, the presence of profound lymphopenia was unappreciated. Eventually a diagnosis of SCID in association with adenosine deaminase deficiency was made. This case serves to emphasize the importance of newborn screening for SCID in the context of careful evaluation of clinical and laboratory findings that may be overlooked and result in a delay in the diagnosis of a potentially life-threatening condition.