Non-classical 1p36 deletion in a patient with Duane retraction syndrome: case report and literature review
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CASE REPORT
Non‑classical 1p36 deletion in a patient with Duane retraction syndrome: case report and literature review Emiy Yokoyama1, Camilo E. Villarroel1, Sinhué Diaz2, Victoria Del Castillo1, Patricia Pérez‑Vera3, Consuelo Salas3, Samuel Gómez4, Reneé Barreda1, Bertha Molina5 and Sara Frias5,6*
Abstract Background: Monosomy of 1p36 is considered the most common terminal microdeletion syndrome. It is character‑ ized by intellectual disability, growth retardation, seizures, congenital anomalies, and distinctive facial features that are absent when the deletion is proximal, beyond the 1p36.32 region. In patients with proximal deletions, little is known about the associated phenotype, since only a few cases have been reported in the literature. Ocular manifestations in patients with classical 1p36 monosomy are frequent and include strabismus, myopia, hypermetropia, and nystagmus. However, as of today only one patient with 1p36 deletion and Duane retraction syndrome (DRS) has been reported. Case presentation: We describe a patient with intellectual disability, facial dysmorphism, and bilateral Duane retrac‑ tion syndrome (DRS) type 1. Array CGH showed a 7.2 Mb de novo deletion from 1p36.31 to 1p36.21. Discussion: Our patient displayed DRS, which is not part of the classical phenotype and is not a common clinical feature in 1p36 deletion syndrome; we hypothesized that this could be associated with the overlapping deletion between the distal and proximal 1p36 regions. DRS is one of the Congenital Cranial Dysinnervation Disorders, and a genetic basis for the syndrome has been extensively reported. The HES3 gene is located at 1p36.31 and could be asso‑ ciated with oculomotor alterations, including DRS, since this gene is involved in the development of the 3rd cranial nerve and the 6th cranial nerve’s nucleus. We propose that oculomotor anomalies, including DRS, could be related to proximal 1p36 deletion, warranting a detailed ophthalmologic evaluation of these patients. Keywords: 1p36 deletion, HES3 gene haploinsufficiency, Duane retraction syndrome Background 1p36 monosomy is the most common terminal microdeletion syndrome, with an incidence of 1 in every 5000 to 10,000 newborns and is found in more than 1.2% of patients with idiopathic intellectual disability [1]. Although the diagnosis may be suspected clinically, it is often confirmed after the application of molecular *Correspondence: [email protected] 6 Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Avenida IMAN No. 1, Torre de Investigación, Insurgentes Cuicuilco, Coyoacán, 04530 Mexico City, Mexico Full list of author information is available at the end of the article
cytogenetic tests. Most cases are de novo with a microdeletion size of approximately 5 Mb, ranging from 1.5 to 10.5 Mb [2, 3]. The classical phenotype is associated with distal deletion of the most terminal chromosomal band (1p36.3) and includes intellectual disability, growth retardation, microcephaly, a distinctive craniofacial dy
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