Localization of the Gene for Hyperostosis Cranialis Interna to Chromosome 8p21 with Analysis of Three Candidate Genes

Hyperostosis cranialis interna (HCI) is a rare autosomal dominant disorder characterized by intracranial hyperostosis and osteosclerosis, which is confined to the skull, especially the calvarium and the skull base. The rest of the skeleton is not affected. Progressive bone overgrowth causes nerve entrapment that leads to recurrent facial nerve palsy, disturbance of the sense of smell, hearing and vision impairments, impairment of facial sensibility, and disturbance of balance due to vestibular areflexia. The treatment is symptomatic. Histomorphological investigations showed increased bone formation with a normal tissue structure. Biochemical parameters were normal. Until today the disease has been described in only three related Dutch families with common progenitors and which consist of 32 individuals over five generations. HCI was observed in 12 family members over four generations. Patients are mildly to severely affected. Besides HCI, several bone dysplasias with hyperostosis and sclerosis of the craniofacial bones are known. Examples are Van Buchem disease, sclerosteosis, craniometaphyseal dysplasia, and Camurati-Engelmann disease. However, in these cases the long bones are affected as well. Linkage analysis in a family with HCI resulted in the localization of the disease-causing gene to a region on chromosome 8p21 delineated by markers D8S282 and D8S382. Interesting candidate genes in this region are BMP1, LOXL2, and ADAM28. Sequence analysis of these genes did not reveal any putative mutations. This suggests that a gene not previously involved in a sclerosing bone dysplasia is responsible for the abnormal growth in the skull of these patients.