Osteochondrodysplasias involve abnormal bone or cartilage growth, leading to skeletal maldevelopment, often short-limbed dwarfism. Diagnosis is by physical examination, x-rays, and, in some cases, genetic testing. Treatment is surgical.
The basic genetic defects have been identified in most of the osteochondrodysplasias. The mutations typically cause perturbation of function in proteins involved in growth and development of connective tissue, bone, or cartilage ( see Table: Types of Osteochondrodysplastic Dwarfism).
Dwarfism is markedly short stature (adult height < 4 ft 10 in) frequently associated with disproportionate growth of the trunk and extremities.
Achondroplasia is the most common and best-known type of short-limbed dwarfism, but there are many other distinct types, which differ widely in genetic background, course, and prognosis (see table Types of Osteochondrodysplastic Dwarfism). Lethal short-limbed dwarfism (thanatophoric dysplasia, caused by mutations in the same gene as achondroplasia) causes severe chest wall deformities and respiratory failure in neonates, resulting in death.
Diagnosis of Osteochondrodysplasias
X-rays
Characteristic x-ray changes may be diagnostic. A whole-body x-ray of every affected neonate, even if stillborn, should be taken because diagnostic precision is essential for predicting prognosis.
Prenatal diagnosis by fetoscopy or ultrasonography is possible in some cases (eg, when fetal limb shortening is severe).
Standard laboratory tests do not help, but molecular diagnosis is feasible for chondrodysplasias with known molecular defects.
Genetic testing is advised if a diagnosis cannot be made based on clinical grounds or if genetic counseling is desired.
Treatment of Osteochondrodysplasias
Sometimes surgical limb-lengthening, surgical correction of leg bowing, or joint replacement
1) in facilitating bone growth.
An increase in adult height may be achieved by surgical limb-lengthening. Bowlegs can be corrected surgically. In achondroplasia and other nonlethal osteochondrodysplasias, surgery (eg, hip replacement) can help improve joint function.
Hypoplasia of the odontoid process can predispose to subluxation of the first and second cervical vertebrae and compression of the spinal cord. Therefore, the odontoid process should be evaluated preoperatively and, if it is abnormal, the patient’s head should be carefully supported when hyperextended for endotracheal intubation during anesthesia.
Because the inheritance pattern and gene mutations in most types are known, genetic counseling can be effective.
Organizations such as Little People of America provide resources for affected people and act as advocates on their behalf. Similar societies are active in other countries.
Treatment reference
1. Savarirayan R, Irving M, Bacino CA, et al: C-type natriuretic peptide analogue therapy in children with achondroplasia. N Engl J Med 381(1):25–35, 2019. doi: 10.1056/NEJMoa1813446
Key Points
Osteochondrodysplasias are inherited abnormalities of growth and development of connective tissue, bone, and/or cartilage.
There are many types, which differ widely in genetic background, course, and prognosis, but all cause markedly short stature and often disproportionate growth of the trunk and extremities.
Diagnosis is by clinical manifestations and identification of characteristic x-ray changes.
Growth hormone treatments are typically ineffective.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
Little People of America: An organization providing community resources and medical support and information to people of short stature
