Hematopoietic stem cell transplantation as treatment for patients with DOCK8 deficiency.

BACKGROUND: Biallelic variations in the DOCK8 gene cause a combined immunodeficiency with eczema, recurrent bacterial and viral infections, and malignancy. Natural disease outcome is dismal, but allogeneic hematopoietic stem cell transplantation (HSCT) can cure the disease.

OBJECTIVE: To determine outcome of HSCT for DOCK8 deficiency and define possible outcome variables.

METHODS: We performed a retrospective study of the results of HSCT in a large international cohort of DOCK8 deficient patients.

RESULTS: We identified 81 patients from 22 centers transplanted at a median age of 9.7 years (range: 0.7-27.2) between 1995 and 2015. After median follow-up of 26 months (3-135), 68 of 81 patients are alive (84%). Severe acute (III-IV) or chronic graft versus host disease (GVHD) occurred in 11% and 10% respectively. Causes of death wereinfections (n=5), GVHD (5), multi-organ failure (2) and pre-existent lymphoma (1). Survival after matched related (n=40) or unrelated (35) HSCT was 89% and 81%, respectively. Reduced toxicity conditioning based on either treosulfan or reduced-dose busulfan resulted in superior survival compared to fully myeloablative busulfan-based regimens (97% vs. 78%; p=0.049). 96% of patients aged <8 years at HSCT survived, compared to 78% of those ≥8 years (p=0.06). Of 73 patients with chimerism data available, 65 (89%) had >90% donor T-cell chimerism at last follow-up. Not all disease manifestations responded equally well to HSCT: eczema, infections and Mollusca resolved better than food allergies or failure to thrive.

CONCLUSION: HSCT is curative in most DOCK8 deficient patients, confirming this approach as the treatment of choice. HSCT using a reduced toxicity regimen may offer the best chance for survival.