A novel mutation in MYCN gene causing congenital absence of the flexor pollicis longus tendon as an unusual presentation of Feingold syndrome 1

Feingold syndrome 1 (FGLDS1) is an autosomal dominant malformation syndrome, characterized by skeletal anomalies, microcephaly, facial dysmorphism, gastrointestinal atresias and learning disabilities. Mutations in the MYCN gene are known to be the cause of this syndrome. Congenital absence of the flexor pollicis longus (CAFPL) tendon is a rare hand anomaly. Most cases are sporadic and no genetic variants have been described associated with this abnormality. We describe here a pedigree combining familial CAFPL tendon as a feature of FGLDS1. Molecular analyses of whole exome sequence data in five affected family members spanning three generations of this family revealed a novel mutation in the MYCN gene (c.1171C>T; p.Arg391Cys). Variants in MYCN have not been published in association with isolated or syndromic CAFPL tendon, nor has this been described as a skeletal feature of Feingold syndrome. This report expands on the clinical and molecular spectrum of MYCN-related disorders and highlights the importance of MYCN protein in normal human thumb and foramen development.