Nicotinic Receptor Mutation in a Mildly Dysmorphic Girl with Duane Retraction Syndrome

Background: To evaluate possible monogenic and chromosomal anomalies in a patient with unilateral Duane retraction syndrome and modest dysmorphism. Materials and Methods: Clinical evaluation, sequencing of candidate genes, and array comparative genomic hybridization (array CGH). Results: The proband had unilateral Duane retraction syndrome (DRS) with low-set ears bilaterally, a high arched palate, and clinodactyly. Motor development and cognitive function were normal. Parents were first cousins, but no other family member was similarly affected. No mutations were detected in the HOXA1. KIF21A. SALL4, TUBB3, and CHN1 genes. Array CGH revealed a 16Kb de novo deletion at chromosome 8p11.2 that encompassed a portion of only one gene, the Cholinergic Receptor, Nicotinic, Beta-3 (CHRNB3, Neuronal). This gene encodes a protein that is involved in the nicotinic acetylcholine receptor on neurons. It interacts functionally with other genes that code components of the acetylcholine receptor. Conclusions: This patient's chromosomal abnormality affected only one gene that is highly expressed in the brainstem and brain, involved in neurotransmission, and could be related to her Duane retraction syndrome.