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Osteochondrodysplasias

(Genetic Skeletal Dysplasias)

by David D. Sherry, MD, Frank Pessler, MD, PhD

Osteochondrodysplasias are a group of rare hereditary disorders of connective tissue, bone, or cartilage that cause the skeleton to develop abnormally.

In osteochondrodysplasias, the growth and development of bone, cartilage, and/or connective tissue is impaired.

Each type of osteochondrodysplasia causes different symptoms. Osteochondrodysplasias usually cause short stature (dwarfism). Some cause more shortening of the limbs than the trunk (short-limbed dwarfism), whereas others cause more shortening of the trunk than the limbs. The most common and best-known type of short-limbed dwarfism is called achondroplasia. There is a lethal form of short-limbed dwarfism called thanatophoric dysplasia that causes severe deformities of the chest and respiratory failure in newborns, which results in death. Some children and adults have short limbs, bowlegs, a bulky forehead, an unusually shaped nose (saddle nose), and an arched back. Sometimes joints do not develop their full range of motion.

Diagnosis

  • X-rays

  • Tests before birth

A doctor usually bases the diagnosis on the symptoms, physical examination, and x-rays of the bones.

Sometimes the abnormal genes responsible for osteochondrodysplasias can be detected, usually by a blood test. Analyzing the genes is most helpful for predicting the disease before birth.

Diagnosis of severe types before birth is also possible using other methods. In some cases, the fetus can be directly viewed with a flexible scope (fetoscopy), or ultrasonography (see Procedures : Ultrasonography) is done.

Treatment

  • Replacement of joints

  • Sometimes lengthening of limbs

If joint movement is severely restricted, surgery may be needed to replace joints such as the hip with artificial ones. Doctors may be able to increase a person’s adult height by doing a surgical procedure to lengthen the limbs.

Because the basic genetic defects have been identified in most of the osteochondrodysplasias, genetic counseling can be effective. Organizations such as Little People of America ( www.lpaonline.org ) provide resources for affected people and act as advocates on their behalf. Similar societies are active in other countries.