Filamin B (FLNB)-Related Spondylocarpotarsal Synostosis Syndrome: Systematic Literature Review and Novel Case Report

Spondylocarpotarsal synostosis syndrome (SCT) is a rare autosomal recessive skeletal dysplasia caused by biallelic loss-of-function variants in FLNB, characterized by disproportionate short stature, progressive vertebral fusion, scoliosis, and carpal (typically capitate-hamate) synostosis, classically without rib anomalies. We performed a systematic literature search of PubMed/MEDLINE and Scopus, supplemented by citation searching, following the PRISMA 2020 statement, to identify all reports providing original, molecularly confirmed FLNB-related SCT patient data. Eleven eligible publications, spanning Taiwanese, Argentinian, Pakistani, Italian, German and Indian cohorts, were included in a qualitative synthesis together with a novel case. The novel patient, an adopted child of Indian origin, presented with severe disproportionate short stature, multisegmental vertebral fusion and posterior arch clefts extending from the cervical to the sacral spine, coccygeal dysgenesis, capitate-hamate fusion, and global developmental delay; targeted exome sequencing identified a novel homozygous frameshift FLNB variant. Integration of this case with the reviewed literature confirms disproportionate short stature, contiguous vertebral fusion, and carpal synostosis as near-universal core features, while tarsal fusion, hearing loss, and facial dysmorphism are variably present. The extent and multisegmental pattern of axial involvement in our patient appear more severe than in most previously reported cases, broadening the recognized phenotypic spectrum of FLNB-related SCT and reinforcing the need for structured, multidisciplinary long-term follow-up.