IGSF1 and congenital nystagmus: The deleted region contains – besides five genes so far unassociated with disease (ENOX2, ARHGA36, OR13H1, FIRRE, MST4) – FRMD7 and IGSF1, loss-of-function mutations in which are known to cause, respectively, congenital nystagmus [2] and the ensemble of central hypothyroidism, hypoprolactinemia and testicular enlargement [3].