Spontaneous resolution of severe idiopathic T cell lymphopenia

Saddiq B. Habiballah, Division of Immunology, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States of America. Electronic address: saddiq.habiballah@childrens.harvard.edu.
Jennifer S. Whangbo, Division of Hematology-Oncology, Boston Children's Hospital, Boston, MA, United States of America; Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA, United States of America.
Ivan D. Cardona, Department of Pediatrics, Maine Medical Center Research Institute, Portland, ME, United States of America.
Craig D. Platt, Division of Immunology, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States of America. Electronic address: craig.platt@childrens.harvard.edu.

Abstract

Potential etiologies of TBNK SCID include both hematopoietic defects and thymic aplasia. The management of patients with this phenotype, identified by newborn screen, may be unclear in the absence of a genetic diagnosis. We report an infant with lymphocyte flow cytometry consistent with TBNK SCID and reduced proliferative response to phytohemagglutinin. The patient had no genetic diagnosis after targeted panel and exome sequencing. The decision to trend laboratory values rather than move immediately to hematopoietic cell transplant was made given the absence of a genetic defect and the finding of a normal thymus on ultrasound. During the course of evaluation for transplant, the patient unexpectedly had normalization of T cell number and function. This case demonstrates a role for mediastinal ultrasound and the utility of trending laboratory values in patients with severe T cell lymphopenia but no genetic diagnosis, given the small but important possibility of spontaneous resolution.