Hematopoietic stem cell transplantation rescues the hematological, immunological and vascular phenotype in DADA2

Deficiency of adenosine deaminase 2 (DADA2) is caused by biallelic deleterious mutations in CECR1 . DADA2 results in variable autoinflammation and vasculopathy (recurrent fevers, livedo reticularis, polyarteritis nodosa, lacunar ischemic strokes and intracranial hemorrhages), immunodeficiency and bone marrow failure. TNF-α blockade is the treatment of choice for the autoinflammation and vascular manifestations. Hematopoietic stem cell transplantation (HSCT) represents a potential definitive treatment. We present a cohort of 14 patients from 6 countries who received HSCT for DADA2. Indication for HSCT was bone marrow dysfunction or immunodeficiency. Six of 14 patients had vasculitis pre-HSCT. The median age at HSCT was 7.5 years. Conditioning regimens were myeloablative (9), and reduced intensity (5). Donors were HLA-matched sibling (n=1), HLA-matched unrelated (n=9), HLA-mismatched unrelated (n=3), and HLA haploidentical sibling (n=1). All patients are alive and well with no new vascular events and resolution of hematological and immunological phenotype at a median follow-up of 18mo (range 5mo to 13yr). Plasma ADA2 enzyme activity normalized in those tested post-HSCT (7/7), as early as D+14 (myeloid engraftment). Post-HSCT hematological autoimmunity (cytopenias) was reported in 4 patients, acute graft versus host disease (GvHD) grade 1 in 2, grade 2 in 3 and grade 3-4 in 1, and moderate chronic GvHD in 1 patient. In conclusion, in 14 patients, HSCT was an effective and definitive treatment for DADA2.