Successful Hematopoietic Stem Cell Transplant in a Patient with Omenn Syndrome: A Case Report

Omenn syndrome is a rare subtype of severe combined immunodeficiency. Affected patients present recurrent infections, lymphadenopathy, skin eruptions, eosinophilia, hepatosplenomegaly, failure to thrive, and gastrointestinal complications with variable severity. A 3-month-old female infant, born to consanguineous healthy parents, presented with splenomegaly, erythroderma, failure to thrive, and history of recurrent otitis media, hypothyroidism, and Bacille Calmette-Guerin lymphadenitis following Bacille Calmette-Guerin vaccination. The immunologic workup showed lymphopenia; low levels of CD3(+) T cells, CD4(+) T cells, and CD8(+) T cells; normal levels of CD19(+) B cells and CD16(+)/CD56(+) natural killer cells; hypogammaglobulinemia; and a high level of serum immunoglobulin E. She was clinically diagnosed with T-B+NK+ severe combined immunodeficiency. Genetic study revealed a missense homozygous alteration (c.617G>A, p.Arg206Gln) in exon 5 of the IL7R gene in the patient, as well as carrier states for the same variant in both parents. The patient received a peripheral blood stem cell transplant from a matched unrelated donor. A reduced intensity conditioning regimen was applied, including fludarabine, melphalan, rabbit antithymocyte globulin, and graft-versus-host disease prophylaxis by cyclosporine and mycophenolate mofetil. She clinically improved, and after engraftment the donor chimerism was 100% at 1 year after transplant. Hematopoietic stem cell transplant is a curative therapeutic option for patients with Omenn syndrome and, when combined with an early diagnosis, can prevent complications and improve patient survival.