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Biallelic loss of function variants in the TMCO1 gene have been previously demonstrated to result in cerebrofaciothoracic dysplasia (CFTD; MIM #213980). The phenotype of this condition includes severe intellectual disability, as well as distinctive craniofacial features, including brachycephaly, synophrys, arched eyebrows, "cupid's bow" upper lip, and microdontia. In addition, nonspecific skeletal anomalies are common, including bifid ribs, scoliosis, and spinal fusion. Only 19 molecularly confirmed patients have been previously described. Here, we present four patients with CFTD, including three brothers from a Pakistani background and an additional unrelated white Scottish patient. All share the characteristic craniofacial appearance, with severe intellectual disability and skeletal abnormalities. We further define the phenotype with comparison to the published literature, and present images to define the dysmorphic features in a previously unreported ethnic group. All of our patient series are homozygous for the same c.292_293del (p.Ser98*) TMCO1 pathogenic variant, which has been previously reported only in an isolated Amish population. Thus we provide evidence that CFTD may be more common than previously thought. The patients presented here further delineate the phenotypic spectrum of CFTD and provide evidence for a recurrent pathogenic variant in TMCO1.

Exome sequencing in the context of developmental disorders is a useful technique, but variants found need to be interpreted in the context of detailed phenotypic information. Whole gene deletions and loss-of-function-mutations in the HNRNPU gene have been associated with intellectual disability and seizures in some patients. However, a unifying syndromic phenotype has not been previously elucidated. Here, we report a total of seven patients (six patients identified through the Wellcome Trust Deciphering Developmental Disorders study, with one additional patient), who have heterozygous de novo mutations in HNRNPU. These were found via trio-based exome sequencing. All but one of the mutations is predicted to cause loss-of-function. These patients have dysmorphic features in common, including prominent eyebrows, long palpebral fissures, overhanging columella, and thin upper lip. All patients have developmental delay and intellectual disability (ID), ranging from moderate to severe. Seizures are common from early childhood. These initially occur in the context of febrile episodes. This series demonstrates common phenotypic features, including emerging dysmorphism, associated with heterozygous HNRNPU mutations. This allows us to define a novel neurodevelopmental syndrome, with a likely mechanism of haploinsufficiency.