Phenotype and HOXD13 gene mutation in a big synpolydactyly (SPD) pedigree

Objective: To study the phenotype and HOXD13 gene mutation of a big synpolydactyly (SPD) Pedigree in Henan Province of China. Methods: The SPD pedigree was taken as research subjects; 13 surviving patients were examined clinically; PCR was used to amplify HOXD13 gene first exon and PCR products were sequenced to detect mutations. Results: In the SPD pedigree, the proportion of sick men and women was the same; delivery was continuous, and there was no cross-hereditary, showing autosomal dominant inheritance; patients showed difference degrees of SPD, but there was a big difference in expressivity among patients; there were nine additional trinucleotide repeats in polyalanine coding sequence in the first exon of HOXD13 gene of patients (totally 27 bp); this repetition makes the alanine residues in poly-alanine chain expand from 15 to 24. Conclusion: The SPD pedigree showed autosomal dominant inheritance; patient phenotypes were complex, with obvious differences in expressivity, but explicit rate was 100%; HOXD13 gene was the causative gene for congenital SPD pedigree.