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Disease characteristics

Excerpted from the GeneReview: SOST-Related Sclerosing Bone Dysplasias
SOST-related sclerosing bone dysplasias include sclerosteosis and van Buchem disease; both are disorders of osteoblast hyperactivity. The major clinical features of sclerosteosis are progressive skeletal overgrowth and variable syndactyly, usually of the second (index) and third (middle) fingers. Affected individuals appear normal at birth except for syndactyly. Distinctive facial features including asymmetric mandibular hypertrophy, frontal bossing, and midface hypoplasia are usually apparent by mid-childhood. Hyperostosis of the skull results in narrowing of the foramina, causing entrapment of the seventh cranial nerve (often leading to facial palsy) and entrapment of the eighth cranial nerve (often resulting in deafness in mid-childhood). In sclerosteosis, hyperostosis of the calvarium reduces intracranial volume, increasing the risk for potentially lethal elevation of intracranial pressure. Survival of individuals with sclerosteosis into old age is unusual. The manifestations of van Buchem disease are generally milder than sclerosteosis and syndactyly is absent. Based on a few case reports, it is also likely that the spectrum of SOST-related sclerosing bone dysplasias includes an autosomal dominant form of craniodiaphyseal dysplasia (CDD).

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Clinical features

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  • Elevated alkaline phosphatase
  • Cranial hyperostosis
  • Thickened cortex of long bones
  • Headache
  • Hearing impairment
  • Cranial nerve paralysis
  • Optic atrophy from cranial nerve compression
  • Increased bone mineral density
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