Mutational screening of NRXN1 in 90 TCF4 mutation negative patients and nine families with suspected recessive inheritance of severe intellectual disability did not reveal any point mutation, while in CNTNAP2 the heterozygous mutation c.1083G>A in the splice donor site of exon 7 was found in two patients (C3, C4). This evidence concerns the gene TCF4 and Intellectual disability.