This family contains several mammalian sclerostin (SOST) proteins. SOST is thought to suppress bone formation. Mutations of the SOST gene lead to sclerosteosis, a progressive sclerosing bone dysplasia with an autosomal recessive mode of inheritance. Radiologically, it is characterised by a generalised hyperostosis and sclerosis leading to a markedly thickened and sclerotic skull, with mandible, ribs, clavicles and all long bones also being affected. Due to narrowing of the foramina of the cranial nerves, facial nerve palsy, hearing loss and atrophy of the optic nerves can occur. Sclerosteosis is clinically and radiologically very similar to van Buchem disease, mainly differentiated by hand malformations and a large stature in sclerosteosis patients [1].

1: Increased bone density in sclerosteosis is due to the deficiency of a novel secreted protein (SOST). Balemans W, Ebeling M, Patel N, Van Hul E, Olson P, Dioszegi M, Lacza C, Wuyts W, Van Den Ende J, Willems P, Paes-Alves AF, Hill S, Bueno M, Ramos FJ, Tacconi P, Dikkers FG, Stratakis C, Lindpaintner K, Vickery B, Foernzler D, Van Hul W; Hum Mol Genet 2001;10:537-543. PMID:11181578

2: Bone dysplasia sclerosteosis results from loss of the SOST gene product, a novel cystine knot-containing protein. Brunkow ME, Gardner JC, Van Ness J, Paeper BW, Kovacevich BR, Proll S, Skonier JE, Zhao L, Sabo PJ, Fu Y, Alisch RS, Gillett L, Colbert T, Tacconi P, Galas D, Hamersma H, Beighton P, Mulligan J; Am J Hum Genet 2001;68:577-589. PMID:11179006