The pathogenic variants in the neuroblastoma-amplified sequence (NBAS) are associated with a clinical spectrum involving the hepatic, skeletal, ocular, and immune systems. Here, we report on two unrelated subjects with a complex phenotype solved by whole-exome sequencing, who shared a synonymous change in NBAS that was documented to affect the transcript processing and co-occurring with a truncating change. Starting from these two cases, we systematically assessed the clinical information available for all subjects with biallelic NBAS pathogenic variants (73 cases in total). We revealed a recognizable facial profile (hypotelorism, thin lips, pointed chin, and "progeroid" appearance) determined by using DeepGestalt facial recognition technology, and we provide evidence for the occurrence of genotype-phenotype correlations. Notably, severe hepatic involvement was associated with variants affecting the NBAS-Nter and Sec39 domains, whereas milder liver involvement and immunodeficiency were generally associated with variants located at the N-terminus and C-terminus of the protein. Remarkably, no patient was reported to carry two nonsense variants, suggesting lethality of complete NBAS loss-of-function. 

Microphthalmia with limb anomalies (MLA, OMIM, 206920) is a rare autosomal-recessive disease caused by biallelic pathogenic variants in the SMOC1 gene. It is characterized by ocular disorders (microphtalmia or anophtalmia) and limb anomalies (oligodactyly, syndactyly, and synostosis of the 4th and 5th metacarpals), variably associated with long bone hypoplasia, horseshoe kidney, venous anomalies, vertebral anomalies, developmental delay, and intellectual disability. Here, we report the case of a woman who interrupted her pregnancy after ultrasound scans revealed a depression of the frontal bone, posterior fossa anomalies, cerebral ventricular enlargement, cleft spine involving the sacral and lower-lumbar vertebrae, and bilateral microphthalmia. Micrognathia, four fingers in both feet and a slight tibial bowing were added to the clinical picture after fetal autopsy. Exome sequencing identified two variants in the SMOC1 gene, each inherited from one of the parents: c.709G>T - p.(Glu237*) on exon 8 and c.1223G>A - p.(Cys408Tyr) on exon 11, both predicted to be pathogenic by different bioinformatics software. Brain histopathology showed an abnormal cortical neuronal migration, which could be related to the SMOC1 protein function, given its role in cellular signaling, proliferation and migration. Finally, we summarize phenotypic and genetic data of known MLA cases showing that our case has some unique features (Chiari II malformation; focal neuropathological alterations) that could be part of the variable phenotype of SMOC1-associated diseases.

Copyright © 2018 Elsevier Masson SAS. All rights reserved.