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Craniotubular Dysplasias

By

Frank Pessler

, MD, PhD, Helmholtz Centre for Infection Research

Last full review/revision Oct 2020| Content last modified Oct 2020
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Osteopetroses are familial disorders characterized by increased bone density and abnormal skeletal modeling.

Craniometaphyseal dysplasia

This autosomal dominant disorder Autosomal Dominant Genetic disorders determined by a single gene (Mendelian disorders) are easiest to analyze and the most well understood. If expression of a trait requires only one copy of a gene (one allele)... read more is caused by mutations in the ANKH gene. Paranasal bossing develops during infancy, and progressive expansion and thickening of the skull and mandible distort the jaw and face. The encroaching bone entraps cranial nerves, causing dysfunction. Malocclusion of the teeth Malocclusion Malocclusion is abnormal contact between the maxillary and mandibular teeth. (See also Evaluation of the Dental Patient.) This photo shows misalignment between upper and lower teeth as the jaw... read more Malocclusion may be troublesome; partial sinus obliteration predisposes to recurrent nasorespiratory infection. Height and general health are normal, but progressive elevation of intracranial pressure is a rare, serious complication.

Diagnosis of craniometaphyseal dysplasia is suspected by typical craniofacial abnormalities, which are at times coupled with increased susceptibility to upper respiratory infection, or the disorder may be found during an evaluation for cranial nerve dysfunction that may result from entrapment at the skull base. Typically, plain x-rays are done. X-ray changes are age-related and usually evident by age 5 years. Sclerosis is the main feature in the skull. Long bones have widened metaphyses, appearing club-shaped, particularly at the distal femur. However, these changes are much less severe than those in Pyle disease Metaphyseal dysplasia (Pyle disease) Craniotubular dysplasias are osteopetroses that involve minor osteosclerosis with normal skeletal modeling. Osteopetroses are familial disorders characterized by increased bone density and abnormal... read more . The spine and pelvis are unaffected.

Treatment of craniometaphyseal dysplasia consists of surgical decompression of entrapped nerves and remodeling of severe bony abnormalities; however, regrowth does occur.

Frontometaphyseal dysplasia

The disorder becomes evident during early childhood. The supraorbital ridge is prominent, resembling a knight’s visor. The mandible is hypoplastic with anterior constriction; dental anomalies are common. Deafness develops during adulthood because sclerosis narrows the internal acoustic foramina and middle ear or may cause deformities of the ossicles. Long leg bones are moderately bowed. Progressive contractures in the digits may simulate arthritis. Height and general health are normal.

Diagnosis of frontometaphyseal dysplasia is suspected by hearing loss in a patient with features of the skeletal abnormalities described previously. Typically, plain x-rays are done. On x-ray examination, bony overgrowth of the frontal region is obvious; patchy sclerosis is seen in the cranial vault. Vertebral bodies are dysplastic but not sclerotic. Iliac crests are abruptly flared, and pelvic inlet is distorted. Femoral capital epiphyses are flattened, with expansion of the femoral heads and coxa valga (hip deformity). Finger bones are undermodeled, with erosion and loss of joint space.

Corrective surgery is indicated for severely disfiguring deformities, including severe micrognathia Micrognathia (small mandible) The jaw can be missing, deformed, or incompletely developed at birth. (See also Introduction to Congenital Craniofacial and Musculoskeletal Disorders and Overview of Congenital Craniofacial... read more Micrognathia (small mandible) , or those causing orthopedic problems. Hearing loss is treated with hearing aids.

Metaphyseal dysplasia (Pyle disease)

The diagnosis of metaphyseal dysplasia is usually made when x-rays are done for an unrelated reason. X-ray changes are striking. Long bones are undermodeled, and bony cortices are generally thin. Tubular leg bones have gross Erlenmeyer flask flaring, particularly in the distal femur. Pelvic bones and thoracic cage are expanded. However, the skull is esentially spared.

Treatment of metaphyseal dysplasia is often not necessary but may involve orthodontic treatments for dental malformations or orthopedic surgery for clinically significant skeletal deformities.

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