This comprises a widely variable spectrum of craniofacial malformations, including craniosynostosis, cranial ossification defects with occipital encephaloceles, characteristic facial dysmorphism, joint contractures and fusions, and digit abnormalities, including long slender digits and oligodactyly.67, 68, 69, 70, 71, 72 Although no measurements of RA in patients have been reported, excess embryonic RA-mediated signaling was demonstrated in Cyp26b1−/− mice.73 Here, CYP26B1 is linked to craniosynostosis.