Novel HOXD13 variants in syndactyly type 1b and type 1c, and a new spectrum of TP63-related disorders.

Syndactyly is the most common limb defect depicting the bony and/or cutaneous fusion of digits. Syndactyly can be of various types depending on the digits involved in the fusion. To date, eight syndactyly-associated genes have been reported, of which HOXD13 and GJA1 have been explored in a few syndactyly but most of them have unknown underlying genetics. In the present study HOXD13, GJA1 and TP63 genes have been screened by resequencing in 24 unrelated sporadic cases with various syndactyly. The screening revealed two pathogenic HOXD13 variants, NM_000523:c.500 A > G [p.(Y167C)], and NM_000523:c.961 A > C [p.(T321P)] in syndactyly type 1b and type 1c, respectively. This is the first report to identify HOXD13 pathogenic variant in syndactyly type 1b and third report in syndactyly type 1c pathogenesis. Furthermore, this study also reports a TP63 pathogenic variant, NM_003722:c.953 G > A [p.(R318H)] in Ectrodactyly and Cleft lip and palate (ECLP). In conclusion, the current study expands the clinical spectrum of HOXD13 and TP63-related disorders.