The novel mutation p.Asp315Tyr causes severe hemophilia B by impairing coagulation factor IX expression

•Mutations in F9 gene may either hinders synthesis and secretion of FIX, or impairs its function.•The novel mutation p.Asp315Tyr happens to affect one critical residue of catalytic triad.•The novel mutation p.Asp315Tyr impairs the proper folding and/or destabilize the overall structure of FIX.