Kosaki overgrowth syndrome: A novel pathogenic variant in <scp><i>PDGFRB</i></scp> and expansion of the phenotype including cerebrovascular complications
Alison Foster, Basile Chalot, Thalia Antoniadi, Élise Schaefer, Rebecca Keelagher, Gavin Ryan, Quentin Thomas, Christophe Philippe, Ange‐Line Bruel, Arthur Sorlin, Christel Thauvin‐Robinet, Marc Bardou, Maxime Luu, Véronique Quenardelle, Valérie Wolff, Jessica Woodley, P. Vabres, Derek Lim, Rebecca Igbokwe, Annie Joseph, Harriet Walker, Andrea Jester, Jonathan R. Ellenbogen, Diana Johnson, Bethanie Rooke, Celia Moss, Trevor Cole, Laurence Faivre
Abstract
Heterozygous activating variants in platelet-derived growth factor, beta (PDGFRB) are associated with phenotypes including Kosaki overgrowth syndrome (KOGS), Penttinen syndrome and infantile myofibromatosis (IM). Here, we present three new cases of KOGS, including a patient with a novel de novo variant c.1477A > T p.(Ser493Cys), and the oldest known individual age 53 years. The KOGS phenotype includes characteristic facial features, tall stature, scoliosis, hyperelastic thin skin, lipodystrophy, variable intellectual and neurological deterioration, and abnormalities on brain imaging. Long-term outcome is unknown. Our cases confirm the phenotypic spectrum includes progressive flexion contractures, camptodactyly, widely spaced teeth, and constriction rings. We also propose novel occasional features including craniosynostosis, ocular pterygia, anterior chamber cleavage syndrome, early osteoporosis, increased pigmentation, recurrent haematomas, predisposition to cellulitis, nail dystrophy, carpal tunnel syndrome, recurrent hypoglycaemia in infancy, joint dislocation, and splenomegaly. Importantly, we report fusiform aneurysm of the basilar artery in two patients. Complications include thrombosis and stroke in the oldest reported patient and fatal rupture at the age of 21 in the patient with the novel variant. We conclude that cerebrovascular complications are part of the phenotypic spectrum of KOGS and KOGS-like disorders and suggest vascular imaging is indicated in these patients.