14q13.1-21.1 Deletion Encompassing the HPE8 Locus in an Adolescent With Intellectual Disability and Bilateral Microphthalmia, But Without Holoprosencephaly

Interstitial deletions involving 14q13.1q21.1 are rare. In theliterature at least 10 cases involving this region have beendescribed and all patients showed a phenotype within theholoprosencephaly (HPE) spectrum. Previous studies suggestedtheHPE8region as a candidate locus forHPEat 14q13.Wereportan adolescent with a 14q13.1q21.1 deletion encompassing theHPE8 region associated with intellectual disability (ID), bilateralmicrophthalmia, and coloboma, without cerebral anomaliestypical of HPE. Except for ocular defects (i.e., microphthalmia,coloboma) consistent withHPE-type anomalies, the minor facialdysmorphia was not suggestive for HPE and the absence ofcerebral anomalies should rule out this diagnosis. The deletionof the potential HPE candidate genes NPAS3, EAPP, SNX6, andTULIP1, raises doubts about their pathologic role in determiningHPE. It is likely that deletions of HPE genes are not sufficientto cause HPE, and that multiple genetic, chromosomal, andenvironmental factors interact to determine the variableclinical expression of HPE. This is the first case of a 14q deletionencompassing the HPE8 locus with the only features consistentwithHPE-type anomalies affecting the ocular system (i.e., microphthalmia,coloboma), and without cerebral anomalies specificfor HPE. The inclusion of potential HPE candidate genes in thedeletion raises the question whether this patient is affected by aless severe form of HPE (HPE microform), or whether he has anew ID/MCA deletion syndrome.