A decision tree for the genetic diagnosis of deficiency of adenosine deaminase 2 (DADA2): a French reference centres experience.

Rama M1, Duflos C2, Melki I3,4, Bessis D5, Bonhomme A6, Martin H6, Doummar D7,8, Valence S7, Rodriguez D7,8, Carme E9, Genevieve D10,11, Heimdal K12, Insalaco A13, Franck N14, Queyrel-Moranne V15, Tieulie N15, London J16, Uettwiller F17, Georgin-Lavialle S18, Belot A19, Koné-Paut I20, Hentgen V21, Boursier G1, Touitou I1,10, Sarrabay G22,23.

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Abstract

Deficiency of adenosine deaminase 2 (DADA2) is a recently described autoinflammatory disorder. Genetic analysis is required to confirm the diagnosis. We aimed to describe the identifying symptoms and genotypes of patients referred to our reference centres and to improve the indications for genetic testing. DNA from 66 patients with clinically suspected DADA2 were sequenced by Sanger or next-generation sequencing. Detailed epidemiological, clinical and biological features were collected by use of a questionnaire and were compared between patients with and without genetic confirmation of DADA2. We identified 13 patients (19.6%) carrying recessively inherited mutations in ADA2 that were predicted to be deleterious. Eight patients were compound heterozygous for mutations. Seven mutations were novel (4 missense variants, 2 predicted to affect mRNA splicing and 1 frameshift). The mean age of the 13 patients with genetic confirmation was 12.7 years at disease onset and 20.8 years at diagnosis. Phenotypic manifestations included fever (85%), vasculitis (85%) and neurological disorders (54%). Features best associated with a confirmatory genotype included fever with neurologic or cutaneous attacks (odds ratio [OR] 10.71, p = 0.003 and OR 10.9, p < 0.001), fever alone (OR 8.1, p = 0.01), and elevated C-reactive protein (CRP) level with neurologic involvement (OR 6.63, p = 0.017). Our proposed decision tree may help improve obtaining genetic confirmation of DADA2 in the context of autoinflammatory symptoms. Prerequisites for quick and low-cost Sanger analysis include one typical cutaneous or neurological sign, one marker of inflammation (fever or elevated CRP level), and recurrent or chronic attacks in adults.