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

- This study is the first of its sort in Iran which focuses on the genetic study of a very rare autosomal recessive non-syndromic nail dysplasia (NDNC).
- The results introduce a novel pathogenic variant in the FZD6 gene in NDNC patients.
- The study confirms that phenotype-directed-genotype diagnosis is an efficient approach in the diagnosis of NDNC.
- The molecular findings are useful in downstream clinical utilities such as cascade genetic screening and genetic counselling.

BackgroundNail 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.ObjectiveA large multiplex family with NDNC was referred for genetic counselling. Thorough genetic evaluation was performed.MethodsPCR-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.ResultsA homozygous 1 bp 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.ConclusionsThis 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.