Lodder et al (AJHG 2016 Aug 10 [epub ahead of print] just reported a new genetic syndrome caused by defects in the gene GNB5. Clinical features of this condition include: developmental delay, hypotonia, gastroesophageal reflux, retinal abnormalities, seizures and cardiac sinus-node dysfunction. Clinical expression of this disease is variable, and there appears to be some genotype-phenotype correlation, with loss of function alleles leading to a more severe phenotype. GNB5 encodes for a G protein beta subunit, and participates in inhibitory G protein signaling, and disruption of this gene likely has widespread effects on downstream cellular signaling.
This is an important condition to consider in patients with sinus node dysfunction and multi-system abnormalities, since sinus node dysfunction os relatively uncommon in children.
Hilary Vernon, MD PhD