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Autosomal dominant lateral temporal epilepsy (ADLTE) or autosomal dominant partial epilepsy with auditory features (ADPEAF) is an inherited epileptic syndrome with onset in childhood/adolescence and benign evolution. The hallmark of the syndrome consists of typical auditory auras or ictal aphasia in most affected family members. ADTLE/ADPEAF is associated in about half of the families with mutations of the leucine-rich, glioma-inactivated 1 (LGI1) gene. In addition, de novo LGI1 mutations are found in about 2% of sporadic cases with idiopathic partial epilepsy with auditory features, who are clinically similar to the majority of patients with ADLTE/ADPEAF but have no family history. Twenty-five LGI1 mutations have been described in familial and sporadic lateral temporal epilepsy patients. The mutations are distributed throughout the gene and are mostly missense mutations occurring in both the N-terminal leucine rich repeat (LRR) and C-terminal EPTP (beta propeller) protein domains. We show a tridimensional model of the LRR protein region that allows missense mutations of this region to be divided into two distinct groups: structural and functional mutations. Frameshift, nonsense and splice site point mutations have also been reported that result in protein truncation or internal deletion. The various types of mutations are associated with a rather homogeneous phenotype, and no obvious genotype-phenotype correlation can be identified. Both truncating and missense mutations appear to prevent secretion of mutant proteins, suggesting a loss of function effect of mutations. The function of LGI1 is unclear. Several molecular mechanisms possibly leading to lateral temporal epilepsy are illustrated and briefly discussed.

Aarskog–Scott Syndrome (AAS) is an X-linked disorder characterised by short stature and multiple facial, limb and genital abnormalities. A gene, FGD1, altered in a patient with AAS phenotype, has been identified and found to encode a protein with homology to Rho/Rac guanine nucleotide exchange factors (Rho/Rac GEF). However, since this original report on identification of a mutated FGD1 gene in an AAS patient, no additional mutations in the FGD1 gene have been described. We analysed 13 independent patients with clinical diagnosis of AAS. One patient presented a mutation that results in a nucleotide change in exon 10 of the FGD1 gene (G2559>A) substituting a Gln for Arg in position 610. The mutation was found to segregate with the AAS phenotype in affected males and carrier females in the family of this patient. Interestingly, Arg-610 is located within one of the two pleckstrin homology (PH) domains of the FGD1 gene and it corresponds to a highly conserved residue which has been involved in InsP binding in PH domains of other proteins. The same residue is often mutated in the Bruton’s tyrosine kinase (Btk) gene in patients with an X-linked agammaglobulinemia. The Arg610Gln mutation represents the first case of a mutation in the PH domain of the FGD1 gene and additional evidence that mutations in PH domains can be associated to human diseases.