Purpose: SMARCB1 encodes a subunit of the SWI/SNF complex involved in chromatin remodeling. Pathogenic variants (PV) in this gene can give rise to three conditions. Heterozygous loss-of-function germline PV cause rhabdoid tumor predisposition syndrome and schwannomatosis. Missense PV and small in-frame deletions in exons 8 and 9 result in Coffin–Siris syndrome, which is characterized by intellectual disability (ID), coarse facial features, and fifth digit anomalies. Methods: By a gene matching approach, individuals with a similar SMARCB1 PV were identified. Informed consent was obtained and patient data were collected to further establish genotype–phenotype relationship. Results: A recurrent de novo missense PV (c.110G>A;p.Arg37His) in exon 2 of SMARCB1, encoding the DNA-binding domain, was identified in four individuals from different genetic centers. They shared a distinct phenotype consisting of profound ID and hydrocephalus due to choroid plexus hyperplasia. Other shared features include severe neonatal feeding difficulties; congenital heart, kidney, and eye anomalies; obstructive sleep apnea; and anemia. Conclusion: The p.Arg37His PV in the DNA-binding domain of SMARCB1 causes a distinctive syndrome, likely through a gain-of-function or dominant-negative effect, which is characterized by severe ID and hydrocephalus resulting from choroid plexus hyperplasia. This report broadens the phenotypic spectrum associated with PV in SMARCB1.

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doi.org/10.1038/s41436-018-0079-4, hdl.handle.net/1765/108877
Genetics in Medicine
Erasmus MC: University Medical Center Rotterdam

Diets, I.J. (Illja J.), Prescott, T., Champaigne, N.L. (Neena L.), Mancini, G., Krossnes, B. (Bård), Frič, R. (Radek), … Kleefstra, T. (2018). A recurrent de novo missense pathogenic variant in SMARCB1 causes severe intellectual disability and choroid plexus hyperplasia with resultant hydrocephalus. Genetics in Medicine, (21), 572–579. doi:10.1038/s41436-018-0079-4