[Clinical phenotype and genotype analysis of neuroinflammation, autoinflammation, splenomegaly and anemia syndrome caused by IRAK4 gene variant].

Objective: To summarize the clinical and genetic features of neuroinflammation, autoinflammation, splenomegaly and anemia (NASA) syndrome and investigate the pathogenic mechanism. Methods: The clinical data of 2 patients diagnosed with NASA syndrome at Department of Pediatrics, Peking Union Medical College Hospital were retrospectively analyzed. Variants were identified by gene panel sequencing and confirmed by Sanger sequencing. The function of IRAK4 gene variants was studied in vitro. Results: Among the 2 patients, case 1 was an 8-year-old girl and case 2 was a 10-year-old boy. Both patients presented in early childhood with anemia and hepatosplenomegaly. Case 1 was also experienced recurrent seizures. Laboratory examinations showed elevated inflammatory markers and neuroimaging revealed bilateral basal ganglia calcification. In case 2, anemia and inflammation markers were well controlled after treatment with tocilizumab, while case 1 succumbed to recurrent seizures. Genetic tests verified compound heterozygous variants in IRAK4 gene: case 1 carries a nonsense variant c.592G>T (p.G198X) and a missense variant c.248A>C (p.D83A), which were respectively from the parents; case 2 carries a c.831+3A>G variant and a frameshift variant c.540delT (p.F180Lfs*26), and the former was inherited from the father and the latter from the mother. The reverse transcription and Sanger sequencing results confirmed that c.831+3A>G variant led to exon 7 skipping. In vitro studies indicated that c.592G>T, c.540delT and c.831+3A>G variants resulted in truncated interleukin-1 receptor-associated kinase-4 (IRAK4) protein while c.248A>C do not cause changes in IRAK4 protein expression level and protein length. Conclusions: NASA syndrome should be considered in children with early-onset anemia, hepatosplenomegaly, recurrent seizures, elevated inflammatory markers and intracranial calcification. IRAK4 gene variants may lead to impaired anti-inflammatory function of IRAK4 protein, contributing to the autoinflammatory phenotype.