[Multiple facets of ADA2 deficiency: Vasculitis, auto-inflammatory disease and immunodeficiency: A literature review of 135 cases from literature]

Deficiency of adenosine deaminase 2 (DADA2) is a recently described auto-inflammatory disorder. It is an autosomal recessive inherited disease, caused by mutations in the ADA2 gene (formerly known as CECR1) encoding ADA2 enzyme. Besides its role in the purine metabolism, it has been postulated that ADA2 may act as a growth factor for endothelial cells and in the differenciation of monocytes. Thus, deficiency of ADA2 would lead to endothelial damage and a skewing of monocytes into M1 pro-inflammatory macrophage, causing DADA2 manifestations. Three core clinical features have been described: inflammatory-vascular signs, hematologic abnormalities and immunodeficiency. Clinically, patients display intermittent fever, cutaneous vascular manifestations, such as livedo, ischemic strokes, arthralgia and abdominal pain crisis. Corticosteroids and immunosuppressive agents (i.e. cyclophosphamide, azathioprine, ciclosporin, methotrexate) appear to be poorly effective. Although the mechanism has not been elucidated, anti-TNF agents have been proven efficient in DADA2 and should therefore be used as first line therapy for vasculitis. Role of anti-platelet and anticoagulant therapies in stroke-prophylaxis remains to be discussed, as those patients display a high risk of intracranial bleeding.