Disruption of the IQSEC2 transcript in a female with X;autosome translocation t(X;20)(p11.2;q11.2) and a phenotype resembling X-linked infantile spasms (ISSX) syndrome.

We report on a female patient with severe infantile spasms, profound global developmental arrest, hypsarrhythmia and severe mental retardation, associated with a de novo apparently balanced X;autosome translocation. Her neurological phenotype resembles that of X-linked infantile spasms (ISSX). Molecular study showed that the translocation disrupts a transcript involved in GTPases signalling, IQSEC2, mapped to the Xp11.22 region. Several genes involved in intracellular signalling pathways via Ras-homologous small GTPase have been implicated in X-linked neurological disorders. Expression studies revealed that the murine homolog of this transcript, Iqsec2, is highly expressed in the nervous system from the early stages of development. These data suggest that IQSEC2 could be considered a candidate gene for X-linked neurological disorders.