Clinical findings of 21 previously unreported probands with HNRNPU-related syndrome and comprehensive literature review.

With advances in genetic testing and improved access to such advances, whole exome sequencing is becoming a first-line investigation in clinical work-up of children with developmental delay/intellectual disability (ID). As a result, the need to understand the importance of genetic variants and its effect on the clinical phenotype is increasing. Here, we report on the largest cohort of patients with HNRNPU variants. These 21 patients follow on from the previous study published by Yates et al. in 2017 from our group predominantly identified from the Deciphering Developmental Disorders study that reported seven patients with HNRNPU variants. All the probands reported here have a de novo loss-of-function variant. These probands have craniofacial dysmorphic features, in the majority including widely spaced teeth, microcephaly, high arched eyebrows, and palpebral fissure abnormalities. Many of the patients in the group also have moderate to severe ID and seizures that tend to start in early childhood. This series has allowed us to define a novel neurodevelopmental syndrome, with a likely mechanism of haploinsufficiency, and expand substantially on already published literature on HNRNPU-related neurodevelopmental syndrome.

Clinical and radiographic delineation of odontochondrodysplasia.

The association of dentinogenesis imperfecta (DI) with a distinct form of chondrodysplasia in a boy was reported by Goldblatt et al. [1991; Am J Med Genet 39:170-172] and has been given the name of Goldblatt syndrome or odontochondrodysplasia (ODCD; OMIM#184260). Since the original description, only four further individuals have been reported (one sib pair and two unrelated cases). We report on an additional six individuals, including a second sib pair (brother and sister), with clinical and radiographic features that cluster and thus confirm the nosologic status of this entity. The main radiographic features are congenital platyspondyly with coronal clefts, severe metaphyseal changes particularly of the hands, wrists, and knees, mesomelic limb shortening, and coxa valga. The main physical signs are short stature, joint laxity, narrow chest, scoliosis, and DI. This combination of clinical and radiographic findings allows clear recognition of this syndrome in early childhood. Of note, the signs that are present in the newborn period are not entirely specific and the differential diagnosis includes spondylometaphyseal dysplasia (SMD) Sedaghatian type or platyspondylic lethal dysplasia (PSLD) Torrance type. The occurrence of two sib pairs in a group of only 11 patients suggests an autosomal recessive inheritance pattern. Overmodification of cartilage-extracted collagen 2 has been reported in two sibs, but mutation analysis of COL2A1 as well as of COMP, FGFR3, RMRP, and SBDS in one or more patients have given negative results, and the molecular etiology is as yet unknown.