Kosaki Overgrowth Syndrome: Report of a Family with a Novel PDGFRB Variant.

Heterozygous activating missense variants of PDGFRB are associated with the phenotype of Kosaki overgrowth syndrome (KOGS). Here, we present a family including a father and 2 siblings with a novel variant, c.2567A>T (p.Asn856Ile), localized in the cytoplasmic tyrosine kinase domain, exhibiting a KOGS phenotype. The coarsening of the facial features, enlargement of the hands/feet, and progressive scoliosis started to appear after an average age of 6. There were no signs of thin/fragile skin, premature aging appearance, myofibroma, white matter findings, and intellectual disability in any of them. Corneal pterygium and evidence of cerebral vasculopathy were only detected in the father. One sibling exhibited café-au-lait spots. Posterior fossa enlargement was revealed only in one sibling. KOGS is an extremely rare overgrowth syndrome. No familial cases of KOGS have been reported so far. Hereby, we demonstrated that the features of KOGS can show mild intrafamilial variability, and the risk of vascular complications may arise with age.