SRTD9 is an extremely rare autosomal recessive skeletal ciliopathy. It is characterized by phalangeal cone-shaped epiphyses, chronic renal disease, early-onset retinal dystrophy, and developmental delay. Some patients have short stature, craniosynostosis, cerebellar ataxia, and hepatic fibrosis. Affected children typically present with renal failure. Retinal dystrophy is varied. In some patients, vision loss begins in early infancy and progresses rapidly to complete blindness, while in some cases, adults may retain partial vision.
The syndrome follows an autosomal recessive pattern of inheritance. It is caused by homozygous or compound heterozygous mutations in the IFT140 gene, which encodes one of subunits of the intraflagellar transport (IFT) complex A. In primary cilia, numerous processes involve IFT such as cilia formation and signaling. IFT140, thus, plays a very important role in the proper functioning of ciliated cells. It is also required for the proper assembly of these ciliated cells, especially the cells in the retina.