Abstract:

Objective To summarise the clinical features and genotypic characteristics of three children with adenosine deaminase 2 (ADA2) deficiency and to improve understanding of the disease. Methods The clinical features of three children with ADA2 deficiency were retrospectively analysed and genetically analysed using exome sequencing (ES). The activity of ADA2 enzyme in the plasma of the patients was measured using a kit. The clinical and genotypic features of the disease were summarised. Results All three children in our group had ADA2 gene variants. Case 1 had recurrent fever, rash, and convulsions as the main clinical manifestations, combined with stroke, accompanied by markedly elevated inflammatory indexes, and there were compound heterozygous variants in the ADA2 gene: c.139G>T and c.484T>C variants. Case 2 had recurrent fever and rash as the main clinical manifestations, combined with gastrointestinal perforation and stroke during the course of the disease, with markedly elevated inflammatory indexes. ES identified compound heterozygous variants of c.916C>T and c.1069G>A in the ADA2 gene. In Case 3, the patient had recurrent fever and cough as the main clinical manifestations, combined with myocarditis, accompanied by markedly reduced immune function. ES identified c.849T>G homozygous variants in ADA2 gene; Plasma ADA2 enzyme activity was found to be significantly reduced in case 1 and 2. Conclusion ADA2 deficiency is rare in China, with variable clinical features, and mastering its clinical features and genetic characteristics can help improve the diagnosis level.

Key words: adenosine deaminase type 2 deficiency, ADA2 gene, gene mutation, child