Schmitt Gillenwater Kelly syndrome is a rare autosomal dominant[1] congenital disorder consisting of radial hypoplasia, triphalangeal thumbs, hypospadias, and maxillary diastema.

[1][2] It was first identified by Edward Schmitt, Jay Y. Gillenwater, Thadeus E. Kelly, and John M. Opitz in 1962, where they published their results in a case study.

Although more research is needed, the genetic cause of radial hypoplasia is believed to come from a rare allele of the Sonic hedgehog (Shh) gene.

[3] This gene produces the Shh protein that induces development of the ulna, and the index, middle, ring, and pinky fingers while increasing the expression of fibroblast growth factor (FGF), another signaling molecule, which induces development of the radius and thumb.

[3] Another symptom of the individuals with the syndrome was Bilaterally symmetrical triphalangeal thumbs had three phalanges rather than two, and a longer finger like appearance.

Hypospadias can come about as a result of imbalances in the Wnt, Shh, Hox, and BMP pathways during fetal development.