Proximal symphalangia and stapes ankylosis

Is the Conductive Hearing Loss in NOG-Related Symphalangism Spectrum Disorder Congenital?

We describe a dominant Japanese patient with progressive conductive hearing loss who was diagnosed with NOG-related symphalangism spectrum disorder (NOG-SSD), a spectrum of congenital stapes fixation syndromes caused by NOG mutations. Based on the clinical features, including proximal symphalangism, conductive hearing loss, hyper-opia, and short, broad middle, and distal phalanges of the thumbs, his family was diagnosed with stapes ankylosis with broad thumbs and toes syndrome (SABTT). Genetic analysis revealed a heterozygous substitution in the NOG gene, c.645C>A, p.C215* in affected family individuals. He had normal hearing on auditory brainstem response (ABR) testing at ages 9 months and 1 and 2 years. He was followed up to evaluate the hearing level because of his family history of hearing loss caused by SABTT. Follow-up pure tone average testing revealed the development of progressive conductive hearing loss. Stapes surgery was performed, and his post-operative hearing threshold improved to normal in both ears. According to hearing test results, the stapes ankylosis in our SABTT patient seemed to be incomplete at birth and progressive in early childhood. The ABR results in our patient indicated the possibility that newborn hearing screening may not detect conductive hearing loss in patients with NOG-SSD. Hence, children with a family history and/or known congenital joint abnormality should undergo periodic hearing tests due to possible progressive hearing loss. Because of high success rates of stapes surgeries in cases of SABTT, early surgical interventions would help minimise the negative effect of hearing loss during school age. Identification of the nature of conductive hearing loss due to progressive stapes ankylosis allows for better genetic counselling and proper intervention in NOG-SSD patients.

A comprehensive review of reported heritable noggin-associated syndromes and proposed clinical utility of one broadly inclusive diagnostic term: NOG-related-symphalangism spectrum disorder (NOG-SSD)

The NOG gene encodes noggin, a secreted polypeptide that is important for regulating multiple signaling pathways during human development, particularly in cartilage and bone. The hallmark of NOG-related syndromes is proximal symphalangism, defined by abnormal fusion of the proximal interphalangeal joints of the hands and feet. Many additional features secondary to NOG mutations are commonly but inconsistently observed, including a characteristic facies with a hemicylindrical nose, congenital conductive hearing loss due to stapes fixation, and hyperopia. The variable clinical presentations led to the designation of five different autosomal dominant syndromes, all subsequently found to have resulted from NOG mutations. These include (1) proximal symphalangism; (2) multiple synostoses syndrome 1; (3) stapes ankylosis with broad thumbs and toes; (4) tarsal-carpal coalition syndrome; and (5) brachydactyly type B2. Herein, we review the phenotypic features associated with mutations in the NOG gene, demonstrating the overlapping characteristics of these syndromes. Due to the variable phenotypic spectrum within families and among families with the same mutation, we propose a unifying term, NOG-related symphalangism spectrum disorder (NOG-SSD), to aid in the clinical recognition and evaluation of all affected individuals with these phenotypes. These NOG gene variants are available in a new locus-specific database (https://NOG.lovd.nl).

Stapes ankylosis in a family with a novel NOG mutation: otologic features of the facioaudiosymphalangism syndrome

OBJECTIVE

To report the phenotype-genotype correlation in a Belgian family that was ascertained to have a novel missense mutation in the NOG gene mapping to chromosome 17q22.

STUDY DESIGN

To describe the phenotype, a retrospective case study was performed based on the otologic, audiologic, ophthalmologic, and radiologic data of the mutation carriers of the NOG gene.

SETTING

Tertiary referral center.

PATIENTS

All members of a Belgian kindred who carried the novel missense mutation in the NOG gene (NOG, Trp205Cys [W205C]; 1426G>C).

INTERVENTIONS

Diagnostic otologic and ophthalmologic examination, audiometric analysis, and radiologic imaging.

MAIN OUTCOME MEASURES

Phenotype-genotype correlations.

RESULTS

All five mutation carriers had a typical facies. Bilateral proximal symphalangism and hyperopia were present in 80%. Five of 10 ears also had progressive early-onset conductive hearing loss caused by stapes ankylosis.

CONCLUSIONS

So far, 14 independent NOG mutations have been identified. The autosomal dominant disorder described in the present family was caused by a novel NOG missense mutation (NOG, Trp205Cys [W205C]; 1426G>C). The phenotype correlated well with the facioaudiosymphalangism syndrome. The mutation carriers demonstrated progressive multiple joint fusions, hyperopia, early-onset conductive deafness, and a typical facies.

Teunissen-Cremers Syndrome: A Clinical, Surgical, and Genetic Report

OBJECTIVE

To describe clinical and radiologic features, results of ear surgery, and genetic analysis in three families with Teunissen-Cremers syndrome.

DESIGN

Case series.

SETTING

Tertiary referral center.

BACKGROUND

The NOG gene encodes the protein noggin, which has antagonist action in osteogenesis. Malformation of bones and joints may result from defects in noggin. Teunissen-Cremers syndrome is caused by mutations in the NOG gene. Two mutations in this gene were reported previously. The proximal symphalangism-hearing impairment syndrome, also caused by mutations in the NOG gene, is characterized by proximal symphalangism, conductive hearing loss, and occasionally synostoses.

METHODS

We examined nine affected members of three Dutch families. Reconstructive middle ear surgery was performed in five patients (nine ears), and we sequenced the NOG gene in these families.

RESULTS

Affected members had conductive hearing impairment, hyperopia, and broad thumbs and first toes with brachytelephalangia. Surgery manifested stapes ankylosis with additional incudal fixation frequently in the fossa incudis. Air-bone gaps decreased to less than 10 dB in six ears. Genetic analysis revealed three new mutations in the NOG gene.

CONCLUSION

The Teunissen-Cremers syndrome is an entity in its clinical presentation, distinct from other syndromes with proximal symphalangism and hearing impairment. So far, in five families with Teunissen-Cremers syndrome, four truncating mutations and one amino acid substitution were found in the NOG gene. The majority of other mutations found in this gene are missense mutations, which might result in some residual protein activity. Reconstructive middle ear surgery is an option for treatment.

Characterization of a stapes ankylosis family with a NOG mutation

OBJECTIVE

To characterize the otologic phenotype in a family with autosomal dominant stapes ankylosis, hyperopia, and skeletal abnormalities caused by a mutation in the noggin gene (NOG).

STUDY DESIGN

Case series.

SETTING

Academic tertiary care center.

PATIENTS

Eight affected and 3 unaffected family members.

MAIN OUTCOME MEASURES

History, physical and radiologic examination, and surgical outcomes.

RESULTS

Although affected members were initially presumed to have typical nonsyndromic otosclerosis, the clinical data were most consistent with an autosomal dominant congenital stapes ankylosis syndrome. Eight of eight affected family members had bilateral low-frequency conductive hearing loss. Six of eight underwent fenestration procedures and/or stapedectomies. All members with initial postoperative closure of the air-bone gap returned to their baseline conductive loss within 2 years. Two affected family members had documented maximal conductive hearing loss by age 4, and two members without previous otologic surgery have not experienced sensorineural hearing loss. High-resolution temporal bone computed tomography showed stapes ankylosis and indistinction of the incudomalleal junction bilaterally and bony regrowth over the stapedotomy for those with stapedectomies. Detailed physical and radiologic examination identified multiple other skeletal abnormalities.

CONCLUSIONS

Although this phenotype may present as classic otosclerosis to the otolaryngologist, detailed investigation revealed a congenital stapes ankylosis syndrome. Because is essential in regulating normal bone development and maturation, mutations in this gene may be associated with excessive bony overgrowth and refixation of the stapes footplate after initial successful surgery. Patients with hereditary conductive hearing loss should be assessed to rule out subtle features of a skeletal syndrome.

Proximal symphalangism with "coarse" facial appearance, mixed hearing loss, and chronic renal failure: new malformation syndrome?

A 25-year-old man is described with short stature, moderate mental retardation, an abnormal facial appearance, a webbed neck, skeletal abnormalities including proximal symphalangism of bilateral second through fifth fingers, mixed hearing loss, and slowly progressive, sclerosing nephropathy. He was large at birth with generalized edema, more pronounced around the jaw, neck and the upper part of the body, but became short with increasing age, and currently measures 143 cm (-4.9 SD). He had intermittent proteinuria and slowly progressive deterioration of the renal function. A biopsy of the left kidney showed global glomerular sclerosis with interstitial fibrosis. He was placed on maintenance peritoneal dialysis at age 17 years, and now on hemodialysis. His skeletal abnormalities included, in addition to proximal symphalangism, stenosis of the cervical canal, scoliosis, brachydactyly of the hands, hypoplastic hip joints, and pes valgus. Other abnormalities noted were a communicating defects of the diaphragm (surgically corrected), bilateral inguinal hernia and cryptorchidism. These clinical manifestations indicate a hitherto undescribed combination of manifestations and nephropathy.

Heterozygous mutations in the gene encoding noggin affect human joint morphogenesis

The secreted polypeptide noggin (encoded by the Nog gene) binds and inactivates members of the transforming growth factor beta superfamily of signalling proteins (TGFbeta-FMs), such as BMP4 (ref. 1). By diffusing through extracellular matrices more efficiently than TGFbeta-FMs, noggin may have a principal role in creating morphogenic gradients. During mouse embryogenesis, Nog is expressed at multiple sites, including developing bones. Nog-/- mice die at birth from multiple defects that include bony fusion of the appendicular skeleton. We have identified five dominant human NOG mutations in unrelated families segregating proximal symphalangism (SYM1; OMIM 185800) and a de novo mutation in a patient with unaffected parents. We also found a dominant NOG mutation in a family segregating multiple synostoses syndrome (SYNS1; OMIM 186500); both SYM1 and SYNS1 have multiple joint fusion as their principal feature. All seven NOG mutations alter evolutionarily conserved amino acid residues. The findings reported here confirm that NOG is essential for joint formation and suggest that NOG requirements during skeletogenesis differ between species and between specific skeletal elements within species.

The impact of a syndromal diagnosis on surgery for congenital minor ear anomalies

Between 1964 and 1986, 104 ears of 86 patients with a minor congenital ear anomaly underwent an exploratory tympanotomy at the Institute of Otorhinolaryngology of the University Hospital Nijmegen. A classification of these anomalies is proposed based on the surgical findings and results. The 4 groups in this classification are: isolated stapes ankylosis, stapes ankylosis associated with an anomaly of the malleus and incus, an isolated anomaly of the malleus and incus with a mobile stapes footplate and finally, aplasia of the oval and/or round window. In a total of 29 ears (22 patients) out of these 104 ears, the anomaly formed part of a syndrome. The various syndromes and the anomalies encountered are discussed. The impact of a syndromal diagnosis on the outcome of reconstructive ear surgery is discussed per syndrome.

Surgery for congenital stapes ankylosis with an associated congenital ossicular chain anomaly

The surgical findings and results are presented on 32 ears with congenital stapes ankylosis with an associated congenital anomaly of the ossicular chain. One third of the patients had a syndromal diagnosis. In 26 ears, stapedectomy could be performed. In 2 other ears, stapes ankylosis to the bony facial canal was mobilized successfully. In the 4 remaining ears, surgical intervention had to be limited to an exploratory tympanotomy for various reasons. The average hearing gain was 23 dB for the 28 ears on which stapes surgery had been performed. A substantial hearing gain of at least 15 dB was achieved in 19 of these 28 ears (68%). The end result was limited to a small extent by an average preoperative sensorineural component of 16 dB in the hearing loss. A review of the findings and results from other larger series in the literature are presented.