Hematopoietic Cell Transplantation Cures Adenosine Deaminase 2 Deficiency: Report on 30 Patients

PURPOSE

Deficiency of adenosine deaminase 2 (DADA2) is an inherited inborn error of immunity, characterized by autoinflammation (recurrent fever), vasculopathy (livedo racemosa, polyarteritis nodosa, lacunar ischemic strokes, and intracranial hemorrhages), immunodeficiency, lymphoproliferation, immune cytopenias, and bone marrow failure (BMF). Tumor necrosis factor (TNF-α) blockade is the treatment of choice for the vasculopathy, but often fails to reverse refractory cytopenia. We aimed to study the outcome of hematopoietic cell transplantation (HCT) in patients with DADA2.

METHODS

We conducted a retrospective study on the outcome of HCT in patients with DADA2. The primary outcome was overall survival (OS).

RESULTS

Thirty DADA2 patients from 12 countries received a total of 38 HCTs. The indications for HCT were BMF, immune cytopenia, malignancy, or immunodeficiency. Median age at HCT was 9 years (range: 2-28 years). The conditioning regimens for the final transplants were myeloablative (n = 20), reduced intensity (n = 8), or non-myeloablative (n = 2). Donors were HLA-matched related (n = 4), HLA-matched unrelated (n = 16), HLA-haploidentical (n = 2), or HLA-mismatched unrelated (n = 8). After a median follow-up of 2 years (range: 0.5-16 years), 2-year OS was 97%, and 2-year GvHD-free relapse-free survival was 73%. The hematological and immunological phenotypes resolved, and there were no new vascular events. Plasma ADA2 enzyme activity normalized in 16/17 patients tested. Six patients required more than one HCT.

CONCLUSION

HCT was an effective treatment for DADA2, successfully reversing the refractory cytopenia, as well as the vasculopathy and immunodeficiency.

CLINICAL IMPLICATIONS

HCT is a definitive cure for DADA2 with > 95% survival.

Life-Prolonging Effects of Adipose Tissue-Derived Stem Cell Transplantation into Mice Exposed to a Lethal Dose of X-Rays

In the event of a high-dose radiation exposure accident, adipose-derived stem cell (ADSC) transplantation might be used as an emergency medical treatment to compensate for bone marrow failure. To investigate the possible course of that treatment, we examined whether transplantation of ADSCs into whole-body X-ray irradiated mice would provide resistance to radiation damage. ADSCs were obtained from a primary culture of adipocytes from adipose tissue of syngeneic mice. The ADSCs were transplanted via an intravenous (i.v.) route after whole-body irradiation (6 Gy, X-rays) of the ICR mice. Fifty days after transplantation, the survival rate of the transplanted group was 40% higher than the control group, and the difference in survival rates was maintained in the following 200 days. After 400 days, however, the difference in survival rates became smaller and disappeared after 650 days. The results indicate that ADSC transplantation may reduce lethality from acute radiation bone marrow injury for several hundred days.

Clinical Applications and Utility of a Precision Medicine Approach for Patients With Unexplained Cytopenias

OBJECTIVE

To demonstrate experience and feasibility of a precision medicine approach for patients with unexplained cytopenias, defined as low blood counts in one or more cell lineages, persistent for 6 months or longer, in the absence of known nutritional, autoimmune, infectious, toxic, and neoplastic (secondary) causes.

PATIENTS AND METHODS

Patients were evaluated in our clinic between November 8, 2016, and January 12, 2018. After a thorough evaluation of known causes, family history, and appropriate clinical assays, genomic evaluation was performed in a stepwise manner, through Sanger, targeted, and/or whole-exome sequencing. Variants were analyzed and discussed in a genomics tumor board attended by clinicians, bioinformaticians, and molecular biologists.

RESULTS

Sixty-eight patients were evaluated in our clinic. After genomic interrogation, they were classified into inherited bone marrow failure syndromes (IBMFS) (n=24, 35%), cytopenias without a known clinical syndrome which included idiopathic and clonal cytopenias of undetermined significance (CCUS) (n=30, 44%), and patients who did not fit into the above two categories ("others," n=14, 21%). A significant family history was found in only 17 (25%) patients (9 IBMFS, 2 CCUS, and 6 others), whereas gene variants were found in 43 (63%) patients (34 [79%] pathogenic including 12 IBMFS, 17 CCUS, and 5 others]. Genomic assessment resulted in a change in clinical management in 17 (25%) patients, as evidenced by changes in decisions with regards to therapeutic interventions (n=8, 47%), donor choice (n=6, 35%), and/or choice of conditioning regimen for hematopoietic stem cell transplantation (n=8, 47%).

CONCLUSION

We show clinical utility of a real-world algorithmic precision medicine approach for unexplained cytopenias.