Autosomal dominant stapes fixation, syndactyly, and symphalangism in a family with NOG mutation: Long term follow-up on surgical treatment

Objective: Evaluation of clinical findings and audiological outcome after surgery in a Danish family with autosomal dominant facio-audio-symphalangism syndrome with stapes fixation, syndactyly and symphalangism. Methods: Retrospective report on eight affected family members in a Danish family. Clinical investigation included X-ray, audiology and in one case video-recorded surgery. Main outcome measure was audiologic results after stapedectomy. Sanger DNA sequencing of NOG was performed on peripheral blood. Results: Audiologic analysis showed that seven of eight affected family members had bilateral conductive hearing loss. Three patients were treated with stapedectomy, on one or both ears, due to fixation of stapes. All the affected members had syndactyly and symphalangism. A not previously reported mutation in the NOG gene (c.688_699del, p.Cys230_Cys232delins11) was found to segregate with the stapes fixation, syndactyly, and symphalangism. p.Cys230_Cysdelins11 was classified as likely pathogenic according to guidelines from the American College of Medical Genetics and Genomics. Conclusion: The clinical presentation of the reported mutation corresponds with previous case reports of families with NOG mutation. In this family, surgery with stapedectomy had lasting effect without renewed fixation of the stapes in a follow up period of 18 months–38 years.