Genetics of human isolated hereditary nail disorders

A novel pathogenic variant in the FZD6 gene causes recessive nail dysplasia in a Moroccan family

This report describes a patient with a novel homozygous nonsense variant, nail dysplasia and diabetes. Only a few patients have been described with FZD6 mutations and nail dysplasia, and the spectrum of associated manifestations has not been identified. Indeed, it is questionable whether there is a link between pancreatic involvement and the genetic abnormality identified.

Congenital Nail Disorders among Children with Suspected Ectodermal Dysplasias

We report on a cohort of 204 children referred between January 2017 and January 2022 to the German Center for Ectodermal Dysplasias, Erlangen. The most frequent reasons for referral were tooth malformations and lack of multiple teeth leading to the suspicion of an ectodermal dysplasia. Many patients also suffered from being unable to perspire. Nail abnormalities, in contrast, represented a much rarer finding, albeit the impact on some individuals was large. As ectodermal dysplasias are congenital genetic conditions affecting the development and/or homeostasis of two or more ectodermal derivatives, including hair, teeth, nails, and certain glands, we analyzed congenital nail disorders detected in these patients. Dystrophic or otherwise abnormal nails were evident in 17 of 18 subjects with pathogenic WNT10A or GJB6 variants but in none of 161 children with EDA variants underlying X-linked hypohidrotic ectodermal dysplasia. However, 2 of 17 children who carry mutations in EDAR or EDARADD, two other genes involved in the ectodysplasin A signaling pathway, showed nail abnormalities, such as brittle or hypoplastic nails. TP63 variants were regularly associated with nail disorders. In one girl, anonychia congenita caused by a compound heterozygous variant of the R-spondin-4 gene (RSPO4) was diagnosed. Thus, nail dysplasia is rarer among patients with ectodermal dysplasia than commonly thought.

Anonychia congenita in different generations of a single Saudi family

Anonychia refers to the absence of nail plates owing to an autosomal dominant or recessive inheritance. Congenital anonychia is a rare condition that may be associated with other ectodermal or mesodermal malformations like epidermolysis bullosa, (deafness, onychodystrophy, osteodystrophy, and mental retardation) syndrome and Iso-Kikuchi syndrome. Here, we report 3 cases with anonychia congenita appearing in different generations of a single family in Kingdom of Saudi Arabia.

What do we learn from dystrophic epidermolysis bullosa, nails only? Idiopathic nail dystrophy may harbor a COL7A1 mutation as the underlying cause

Dystrophic epidermolysis bullosa (DEB) is a genodermatosis caused by mutations in the COL7A1 gene. DEB, nails only (DEB-na), is a rare type of DEB. Patients with DEB-na can be overlooked, and genetic testing is helpful to determine the correct diagnosis. We collected two families with DEB-na. Clinical information was analyzed. Ultrastructural analysis of the skin tissue was performed. Blood samples were obtained. Next-generation sequencing was performed and the results were confirmed by Sanger sequencing. A genetic study revealed two novel heterozygous mutations: COL7A1:c.6742G>A (p.G2248R) in patient 1 and c.7181C>G (p.P2394R) in patient 2. Precise diagnosis was made for every patient based on clinical findings and genetic studies. We summarized the phenotype and COL7A1 mutations related to DEB-na. We report a new phenotype of DEB-na and two novel mutations in COL7A1. In addition, we emphasize the importance of careful clinical examination and genetic testing in the diagnosis of DEB-na.

A possible founder mutation in FZD6 gene in a Turkish family with autosomal recessive nail dysplasia

BACKGROUND

Autosomal recessive nail dysplasia is characterized by thick and hard nails with a very slow growth on the hands and feet. Mutations in FZD6 gene were found to be associated with autosomal recessive nail dysplasia in 2011. Presently, only seven mutations have been reported in FZD6 gene; five mutations are clustered in the C-terminus, one is at the seventh transmembrane domain, and another is at the very beginning of third extracellular loop.

METHODS

Whole exome sequencing (WES) was applied to the index case, her one affected sister and her healthy consanguineous parents. The mutation was verified via Sanger sequencing. Molecular dynamics simulations of the predicted structures of native and mutant proteins were compared to gain insight into the pathogenicity mechanism of the mutation.

RESULTS

Here, we report a homozygous 8 bp deletion mutation, p.Gly559Aspfs*16; c.1676_1683delGAACCAGC, in FZD6 gene which causes a frameshift and creates a premature stop codon at position 16 of the new reading frame. Our molecular dynamics calculations predict that the pathogenicity of this frameshift mutation may be caused by the change in entropy of the protein with negative manner, disturbing the C-terminal domain structure, and hence interaction partners of FZD6.

CONCLUSION

We identified a homozygous deletion mutation in FZD6 in a consanguineous Turkish family with nail dysplasia. We also provide a molecular mechanism about the effects of the deletion on the protein structure and its possible motions. This study provides a pathogenicity mechanism for this mutation in nail dysplasia for the first time.

A novel pathogenic variant in the FZD6 gene causes recessive nail dysplasia in a large Iranian kindred

BACKGROUND

Nail disorder nonsyndromic congenital (NDNC) is a very rare clinically and genetically heterogeneous disease inherited both in recessive or dominant modes. FZD6 is a component of Wnt-FZD signaling pathway in which recessive loss-of-function variants in the corresponding genes could lead to nail anomalies.

OBJECTIVE

A large multiplex family with NDNC was referred for genetic counselling. Thorough genetic evaluation was performed.

METHODS

PCR-Sanger sequencing was carried out for the coding exons and exon-intron boundaries of the FZD6 gene. Co-segregation analysis, in silico evaluation and computational protein modeling was accomplished.

RESULTS

A homozygous 1bp deletion variant, c.1859delC (p.Ser620Cysfs*75), leading to a truncating protein was found in the patient. Parents were heterozygous for the variant. The variant was found to be co-segreagting with the phenotype in the family. Computational analysis and protein modeling revealed its pathogenic consequence by disturbing the cytoplasmic domain structure and signaling through loss of phosphorylation residues. The variant met the criteria of being pathogenic according to the ACMG guideline.

CONCLUSIONS

This is the first report of the genetic diagnosis of NDNC in Iran. We also report a novel pathogenic variant. The study of the FZD6 gene is recommended as the first step in the diagnostic routing of the autosomal recessive NDNC patients with enlarged nails.

Isolated recessive nail dysplasia caused by FZD6 mutations: report of three families and review of the literature

Congenital abnormalities of the nail are rare conditions that are most frequently associated with congenital ectodermal syndromes involving several of the epidermal appendages including the skin, teeth, hair and nails. Isolated recessive nail dysplasia (IRND) is much rarer but has recently been recognized as a condition resulting in 20‐nail dystrophy in the absence of other cutaneous or extracutaneous findings. A few case reports have identified mutations in the Frizzled 6 (FZD6) gene in families presenting with abnormal nails consistent with IRND. These reports have highlighted the role of Wnt–FZD signalling in the process of nail formation. We report three families presenting with features of IRND, in whom we identified mutations in FZD6, including one previously unreported mutation.