DDX58 and Classic Singleton-Merten Syndrome.

Singleton-Merten syndrome manifests as dental dysplasia, glaucoma, psoriasis, aortic calcification, and skeletal abnormalities including tendon rupture and arthropathy. Pathogenic variants in IFIH1 have previously been associated with the classic Singleton-Merten syndrome, while variants in DDX58 has been described in association with a milder phenotype, which is suggested to have a better prognosis. We studied a family with severe, "classic" Singleton-Merten syndrome. We undertook clinical phenotyping, next-generation sequencing, and functional studies of type I interferon production in patient whole blood and assessed the type I interferon promoter activity in HEK293 cells transfected with wild-type or mutant DDX58 stimulated with Poly I:C. We demonstrate a DDX58 autosomal dominant gain-of-function mutation, with constitutive upregulation of type I interferon. DDX58 mutations may be associated with the classic features of Singleton-Merten syndrome including dental dysplasia, tendon rupture, and severe cardiac sequela.