Sensenbrenner syndrome (OMIM #218330) is a rare (less than 20 cases reported by 2010) multisystem disease first described by Judith A. Sensenbrenner in 1975. It is inherited in an autosomal recessive fashion, and a number of genes appear to be responsible. Three genes responsible have been identified: intraflagellar transport (IFT)122 (WDR10), IFT43—a subunit of the IFT complex A machinery of primary cilia, and WDR35 (IFT121: TULP4) It is also known as Sensenbrenner–Dorst–Owens syndrome, Levin syndrome I and cranioectodermal dysplasia (CED) Presentation These are pleomorphic and include dolichocephaly (with or without sagittal suture synostosis) microcephaly pre- and postnatal growth retardation brachydactyly narrow thorax rhizomelic dwarfism epicanthal folds hypodontia and/or microdontia sparse, slow-growing, hyperpigmented, fine hair nail dysplasia hypohydrosis chronic kidney failure heart defects liver fibrosis visual deficits photophobia hypoplasia of the posterior corpus callosum aberrant calcium homeostasis Electroretinography shows gross abnormalities. Two fetuses of 19 and 23 weeks gestation have also been reported. They showed acromesomelic shortening, craniofacial characteristics with absence of craniosynostosis, small kidneys with tubular and glomerular microscopic cysts, persistent ductal plate with portal fibrosis in the liver, small adrenals, an enlarged cisterna magna and a posterior fossa cyst. Cause The gene IFT122 is located on the long arm of chromosome 3 (3q21-3q24). The gene lies on the Watson (plus) strand and is 80,047 bases in length. The encoded protein has 1241 amino acids and a predicted weight of 141.825 kiloDaltons (kDa). It is a member of the WD repeat protein family. WDR35 is also a member of the WD repeat protein family. The gene is located on the short arm of chromosome 2 (2p24.1–2p24.3) The gene lies on the Crick (minus) strand and is 79,745 bases in length. The encoded protein is 1181 amino acids in length and its predicted molecular weight is 133.547 kiloDaltons. The gene IFT43 lies on the Watson (plus) strand of the long arm of chromosome 14 (14q24.3). A mouse model for IFT122 has been created. Mutants deficient in IFT122 show multiple developmental defects (many are lethal), including exencephaly, situs viscerum inversus, delay in turning, hemorrhage and defects in limb development. In the node, primary cilia were absent or malformed in homozygous mutant and heterozygous embryos, respectively. Impairment of the Sonic hedgehog pathway was apparent in both neural tube patterning (expansion of motoneurons and rostrocaudal level-dependent contraction or expansion of the dorsolateral interneurons) and limb patterning (ectrosyndactyly). Pathophysiology The IFT machinery is organized in