sclerosteosis (MONDO_0017838) is a very rare serious sclerosing hyperostosis syndrome characterized clinically by variable syndactyly and progressive skeletal overgrowth (particularly of the skull), resulting in distinctive facial features (mandibular overgrowth, frontal bossing, midfacial hypoplasia), cranial nerve entrapment causing facial palsy and deafness, and potentially lethal elevation of intracranial pressure. Also known as: cortical hyperostosis with syndactyly, cortical hyperostosis-syndactyly syndrome.