HINT1 and Gamstorp-Wohlfart syndrome: Haplotype analysis demonstrated founder effects for four of the recurrent HINT1 mutations in Europe [1, 2, 13] (p.Arg37Pro, p.Cys84Arg, p.Arg95Gln, p.His112Asn) and one in China [9] (p.Cys38Arg) explaining the elevated prevalence of NMAN in certain geographical areas.