Compound heterozygous variants in RAB34 in a rare skeletal ciliopathy syndrome

Skeletal ciliopathies are a heterogenous group of congenital disorders characterized by multiple internal abnormalities, and distinct radiographic presentation. Pathogenic variants in at least 30 cilia genes are known to cause skeletal ciliopathies. Here we report a fetus with an atypical skeletal ciliopathy phenotype and compound heterozygous variants in the RAB34 gene. The affected fetus had multiple malformations, including posterior neck edema, micrognathia, low-set and small ears, auricular hypoplasia, cleft lip and palate, short extremities, and a combination of rarely occurring pre- and postaxial polydactyly. Genome sequencing identified compound heterozygous variants in the RAB34 gene: maternal c.254T>C, p.(Ile85Thr), and paternal c.691C>T, p.(Arg231*) variants. Only the paternal variant was present in the unaffected sibling. Evidence in the literature indicated that Rab34^-/- mice displayed a ciliopathy phenotype with cleft palate and polydactyly. These features were consistent with malformations detected in our patient supporting the pathogenicity of the identified RAB34 variants. Overall, this case report further expands genetic landscape of human ciliopathy syndromes and suggests RAB34 as a candidate gene for skeletal ciliopathies.