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Case Reports in Genetics
Volume 2019, Article ID 2836263, 5 pages
https://doi.org/10.1155/2019/2836263
Case Report

A Start Codon Variant in NOG Underlies Symphalangism and Ossicular Chain Malformations Affecting Both the Incus and the Stapes

1Department of Otolaryngology, Head and Neck Surgery, Baylor College of Medicine, Houston, Texas, USA
2Center for Statistical Genetics, Department of Neurology, Gertrude H. Sergievsky Center, Columbia University Medical Center, New York, NY, USA
3Department of Otolaryngology, Houston Methodist Hospital, Houston, Texas, USA

Correspondence should be addressed to Isabelle Schrauwen; moc.liamg@newuarhcs.ellebasi

Received 5 April 2019; Accepted 11 July 2019; Published 22 July 2019

Academic Editor: Silvia Paracchini

Copyright © 2019 Nathan R. Lindquist et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We performed exome sequencing to evaluate the underlying molecular cause of a patient with bilateral conductive hearing loss due to multiple ossicular abnormalities as well as symphalangism of the fifth digits. This leads to the identification of a novel heterozygous start codon variant in the NOG gene (c.2T>C:p.Met1?) that hinders normal translation of the noggin protein. Variants in NOG lead to a spectrum of otologic, digit, and joint abnormalities, a combination suggested to be referred to as NOG‐related‐symphalangism spectrum disorder (NOG‐SSD). Conductive hearing loss from such variants may stem from stapes footplate ankylosis, fixation of the malleoincudal joint, or fixation of the incus short process. In this case, the constellation of both stapes and incus fixation, an exceptionally tall stapes suprastructure, thickened long process of the incus, and enlarged incus body was encountered, leading to distinct challenges during otologic surgery to improve hearing thresholds. This case highlights multiple abnormalities to the ossicular chain in a patient with a start codon variant in NOG. We provide detailed imaging data on these malformations as well as surgical considerations and outcomes.