STXBP1 and infantile spasms: Another example was a case with infantile spasm that presented a missense mutation in DIAPH3 (p.Arg432Lys) and a nonsense mutation in the syntaxin-binding protein 1 gene (STXBP1) [171], whose mutation is known to cause developmental and epileptic encephalopathy 4 (MIM:602926) [172].