A Familial Case of Thauvin–Robinet–Faivre Syndrome ( TROFAS ), Presenting With Postaxial Polydactyly and Upper Lip Vascular Malformation

ABSTRACT Thauvin–Robinet–Faivre syndrome (TROFAS, OMIM #617107) is a recently identified autosomal recessive disorder characterised by syndromic overgrowth, facial dysmorphism, mild intellectual disability, variable congenital anomalies, and occasional tumour occurrence. TROFAS results from homozygous or compound heterozygous variants in the FIBP gene, encoding the intracellular binding protein for acidic fibroblast growth factor. This protein plays a role in the fibroblast growth factor (FGF) signalling pathway, which is involved in cell proliferation and contributes to the development of several structures, such as the nervous system, optic vesicles, and blood vessels. Prior to the present report, TROFAS has been described in 10 patients from seven families, four of which are of Turkish origin. We report two additional Turkish siblings from a previously unreported family harbouring the recurrent homozygous c.412‐3_415dupCAGTTTG likely pathogenic variant in FIBP . Both presented with typical TROFAS features; however, the male sibling exhibited a more severe neurodevelopmental profile and additional malformations, including postaxial polydactyly and upper lip vascular malformation, which, to our knowledge, have not previously been reported in association with TROFAS. A detailed clinical characterisation of these two new cases contributes to a more comprehensive delineation of the syndrome, adding potentially novel phenotypic features requiring confirmation in additional patients.