Seven additional families with spondylocarpotarsal synostosis syndrome with novel biallelic deleterious variants in FLNB

The location and/or type of variants in FLNB result in a spectrum of osteochondrodysplasias ranging from mild forms, like spondylocarpotarsal synostosis syndrome and Larsen syndrome, to severe perinatal lethal forms, such as atelosteogenesis I and III and Boomerang dysplasia. Spondylocarpotarsal synostosis syndrome is characterized by disproportionate short stature, vertebral anomalies and fusion of carpal and tarsal bones. Biallelic loss-of-function variants in FLNB are known to cause spondylocarpotarsal synostosis syndrome and 9 families and 9 pathogenic variants have been reported so far. We report clinical features of 10 additional patients from 7 families with spondylocarpotarsal synostosis syndrome due to 7 novel deleterious variants in FLNB, thus expanding the clinical and molecular repertoire of spondylocarpotarsal synostosis syndrome. Our report validates key clinical (fused thoracic vertebrae and carpal and tarsal coalition) and molecular (truncating variants in FLNB) characteristics of this condition.