Objective To analyse the epidemiology of otosclerosis in a British cohort collected between 2011 and 2017. Design Retrospective cohort study. Setting Five UK ENT Departments. Patients Patients with surgically confirmed otosclerosis. Main Outcome Measures Questionnaire data documented family history of otosclerosis, age of onset, medical history and information on associated risk factors for 657 patients. Pre and post-surgical pure-tone audiometry was collected for 154 of these patients. Results The age of onset, incidence of bilateral disease, tinnitus and vertigo, a higher prevalence of women (65%) than men (35%) are similar to those reported previously for otosclerosis cohorts. No association with measles infection was detected. Patients with a family history (40%) have an earlier age of onset and a higher incidence of bilateral disease and vertigo than non-familial subjects. Pedigree analysis is consistent with an autosomal dominant inheritance with reduced penetrance being apparent in 44/91 pedigrees studied. Women who associate their hearing loss with pregnancy have an earlier age of onset than those that do not (p=6x10-6). Conclusions This study confirms that otosclerosis is an early adult onset disease that is more prevalent in women than men with a large minority of patients having a family history of otosclerosis. We report new evidence to support a relationship between pregnancy and otosclerosis progression in a proportion of women. In addition, this is the first study to identify differences in severity between familial and non-familial cases of otosclerosis, highlighting the possibility that more than one aetiology may be involved.

Otosclerosis is a common form of hearing loss which typically presents in young adults. The disease has a familial, monogenic form and a non-familial form with a more complex aetiology. A previous genome wide association study identified evidence that variants within RELN are associated with the condition. Other genes in which an association has been reported include BMP2, COL1A1, FGF2, PPP2R5B and TGFB1. However, follow up studies have often failed to replicate initial positive results. The aim of this study was to establish if an association exists between eight single nucleotide polymorphisms (SNPs) in these six previously implicated genes and otosclerosis in a British case–control cohort (n = 748). Evidence of an association between rs1800472 in TGFB1 and otosclerosis was found (p = 0.034), this association was strongest amongst non-familial cases (p = 0.011). No evidence of an association was detected with variants in COL1A1, FGF2, BMP2, and PPP2R5B. No association between variation in RELN and otosclerosis was observed in the whole cohort. However, a significant association (p = 0.0057) was detected between one RELN SNP (rs39399) and otosclerosis in familial patients. Additionally, we identify expression of one RELN transcript in 51 of 81 human stapes tested, clarifying previous conflicting data as to whether RELN is expressed in the affected tissue. Our findings strengthen the association of TGFB1 (rs1800472) with otosclerosis and support a relationship between RELN and familial otosclerosis only, which may explain previous variable replications.

Otosclerosis is a relatively common heterogenous condition, characterized by abnormal bone remodelling in the otic capsule leading to fixation of the stapedial footplate and an associated conductive hearing loss. Although familial linkage and candidate gene association studies have been performed in recent years, little progress has been made in identifying disease-causing genes. Here, we used whole-exome sequencing in four families exhibiting dominantly inherited otosclerosis to identify 23 candidate variants (reduced to 9 after segregation analysis) for further investigation in a secondary cohort of 84 familial cases. Multiple mutations were found in the SERPINF1 (Serpin Peptidase Inhibitor, Clade F) gene which encodes PEDF (pigment epithelium-derived factor), a potent inhibitor of angiogenesis and known regulator of bone density. Six rare heterozygous SERPINF1 variants were found in seven patients in our familial otosclerosis cohort; three are missense mutations predicted to be deleterious to protein function. The other three variants are all located in the 5′-untranslated region (UTR) of an alternative spliced transcript SERPINF1-012. RNA-seq analysis demonstrated that this is the major SERPINF1 transcript in human stapes bone. Analysis of stapes from two patients with the 5′-UTR mutations showed that they had reduced expression of SERPINF1-012. All three 5′-UTR mutations are predicted to occur within transcription factor binding sites and reporter gene assays confirmed that they affect gene expression levels. Furthermore, RT-qPCR analysis of stapes bone cDNA showed that SERPINF1-012 expression is reduced in otosclerosis patients with and without SERPINF1 mutations, suggesting that it may be a common pathogenic pathway in the disease.