Introduction: Noggin encoding (NOG) gene plays a critical role in early embryogenesis and development of bones, joints, cartilage, eyes, and neural tissue. The NOG gene encodes the noggin protein. Noggin is the only secreted inhibitor of bone morphogenetic protein (BMP) that is associated with abnormal phenotypes in humans. The most commonly observed manifestations of NOG gene mutations include bilateral conductive hearing loss, proximal symphalangism, broad thumbs, hyperopia, and a distinct facial appearance. This genetic disorder was first reported in 1990 by Teunissen and Cremers. Since then, various phenotypic presentations of NOG mutation have been reported, leading to the introduction of the term NOG-related symphalangism spectrum disorder (NOG-SSD). Case report: In this report, we describe a family (mother and daughter) with bilateral mixed hearing loss. Both patients had hyperopia, distinct facial appearance with hemicylindrical nose, broad thumbs, and syndactyly of the second and third toes. Genetic testing confirmed a NOG gene mutation. Bilateral stapedotomy was successfully performed, resulting in significant hearing improvement. However, due to sensorineural component of hearing loss, complete hearing recovery was only achieved with the use of hearing aids. Discussion: The etiology of the sensorineural component of hearing loss in NOG-SSD remains unclear. In animal models, the NOG gene is essential for inner ear development, while in humans, only middle ear malformations have been reported. The phenotypic variability observed in individuals with NOG mutations is very wide, suggesting that the sensorineural component of hearing loss could represent one of the possible manifestations. Conclusions: Conductive hearing loss is the primary manifestation of the NOG-SSD, and all previously reported cases of NOG gene mutations have presented exclusively with conductive hearing loss. It is possible that additional genetic factors, not necessarily directly related to the NOG gene but present in this family, contribute to the development of the sensorineural component of hearing loss, although thorough genetic testing did not reveal any additional mutation. This is, to our knowledge, the first report of mixed hearing loss associated with a NOG mutation confirmed preoperatively. Further studies are needed to determine whether the sensorineural component represents a primary manifestation or arises from secondary mechanisms.

Bone Morphogenetic Proteins and the related Growth and Differentiation Factors (GDFs) are much conserved signaling proteins. GDF5 is pivotal for skeletal development. Several skeletal dysplasia and malformation syndromes are known as a result of mutations in GDF5. Multiple Synostosis Syndrome2 (SYNS2) is characterized by tarsal-carpal coalition, humeroradial synostosis, brachydactyly, and proximal symphalangism. In this study, we analyzed a large Iranian pedigree affected with a new type of SYNS2 (Farhud Type) in five successive generations. In this family-based study (1982-2022), Genetic linkage analysis of the pedigree (58affected, 62healthy) excluded the locus on chromosome 17q21-q22 in our previous study. Thus, we focused on 20q11.22 locus and GDF5 gene. Genetic investigations were performed on 16 patients with SYNS2 and 40 healthy individuals. Whole-exome-sequencing results identified a heterozygote missense mutation in exon2 of GDF5 (NG_008076.1:g.9239G>A, NM_000557.2:c.1424G>A, S475N, rs121909347). This mutation was found in all patients but not in the unaffected individuals. This missense mutation is notable because S475 is strictly conserved among different species, and it is located in a highly conserved and active mature domain of GDF5 (phyloP100way=7.64). The corresponding defect in GDF5 may have unknown interaction with normal active 3rd and 4th structure of the product. Further bioinformatics study (amino acid multiple alignments) showed that the S475 is a much-conserved residue in many different species. These results introduce a new role of GDF5 in pathogenesis of a SYNS2 (Farhud Type), considered in genetic counseling, prenatal diagnosis, and as a potential target for molecular therapy, if possible.

To explore the clinical and genetic characteristics of a Chinese pedigree affected with Multiple synostoses syndrome type 1 (SYNS1). Clinical data of the proband and her family members were collected. Genomic DNA was extracted from peripheral blood samples. Whole-exome sequencing (WES) and whole-genome sequencing (WGS) were carried out for the proband and her parents. The pedigree has comprised of 14 members from three generations, of whom six had manifested hearing loss, with other symptoms including proximal symphalangism, hemicylindrical nose, amblyopia, strabismus, brachydactyly, incomplete syndactyly, which fulfilled the diagnostic criteria for SYNS1. WES had detected no pathogenic single nucleotide variants and insertion-deletion (InDel) in the coding region of the NOG gene, whilst copy number variation (CNV) analysis indicated that there was a heterozygous deletion involving the NOG gene. WGS revealed a heterozygous deletion (54171786_55143998) in 17q22 of the proband. The CNV was classified as pathogenic based on the guidelines from the American College of Medical Genetics and Genomics (ACMG). The heterozygous deletion in 17p22 involving the NOG gene probably underlay the pathogenesis of SYNS1 in this pedigree. Above finding has enriched the mutational spectrum of NOG. CNV should be considered when conventional sequencing has failed to detect any pathogenic variants in such patients.

Symphalangism is a rare, congenital syndrome involving ankylosis of the interphalangeal joints. We present a rare case of fracture at the level of a fused proximal interphalangeal joint in a patient with proximal symphalangism of the hand. Nonoperative management with splinting resulted in osseous healing and restored baseline function.

Esophageal atresia and tracheoesophageal fistula (EA/TEF) are relatively common malformations of the human foregut. The etiology remains incompletely understood with genetic causes identified in a small minority of affected patients. We present the case of a newborn with type C EA/TEF along with proximal symphalangism found to have a de novo NOG nonsense mutation. Patients with chromosome 17q deletions including the NOG gene have previously been reported to have EA/TEF but mutations in the gene have not been identified in patients with this malformation. This case provides evidence that haploinsufficiency for NOG may be the cause for EA/TEF in the 17q deletion syndrome and suggests that the clinical spectrum of NOG-related symphalangism spectrum disorders may include EA/TEF.