Proximal symphalangism, hyperopia, conductive hearing impairment, and the NOG gene: 2 new mutations

Abstract

OBJECTIVES: To report on 2 families with proximal symphalangism syndrome and 2 new NOG gene mutations and to report on the outcomes of exploratory tympanotomy. STUDY DESIGN: Retrospective chart study. SETTING: Tertiary referral center. PATIENTS: A total of 6 patients, one of which underwent an exploratory tympanotomy, were examined from 2 families. INTERVENTION: Exploratory tympanotomy in 1 patient. MAIN OUTCOME MEASURES: Medical and otologic histories and postoperative hearing outcomes. RESULTS: In the patient that was operated upon, the preoperative air conduction hearing threshold of 55 dB was reduced to 41 dB with a residual air bone gap of 21 dB. Furthermore, deoxyribonucleic acid analysis revealed 2 different mutations: a heterozygous nonsense mutation in the NOG gene, c.391C>T (p.Gln131X), and a frameshift mutation in the NOG gene (NOG, c.304del (p.Ala102fs)). CONCLUSION: NOG gene mutations, which lead to aberrant noggin protein function, give rise to a large spectrum of clinical findings and different symphalangism syndromes. These syndromes are all allelic disorders within the Noggin phenotype spectrum. We report on 2 new mutations that are supplementary to those previously described in the literature.