This is a group of genetic disorders affecting the growth of the bones and the cartilage leading to skeletal mal-development. There are several types of osteochondrodysplasias that cause dwarfism and achondroplasia is the common forms of short-limbed dwarfism. In most forms of this disorder, genetic defect has been identified to be the cause of it. Some of the types of osteochondrodysplastic dwarfism include hypochondroplasia, diastrophic dysplasia, pseudoachondroplasia and spondyloepiphyseal dysplasia congentita.
Achondroplasia
This is a form of short-limbed dwarfism and develops because of a problem with the conversion of cartilage to bone in a process called ossification. This particularly affects the long bones of the arms and the legs presenting an average adult male height of 4 feet, 4 inches and average female adult height as 4 feet, 1 inch. Other features of this disorder include an average-sized trunk, short arms and legs, limited movements at the elbows and an enlarged head. In addition, they can also exhibit apnea, obesity, recurrent ear infections, bowed legs and abnormal curvature of the spine. An uncommon complication includes the hydrocephalus which is the accumulation of fluid in the brain which can cause large sized head and brain abnormalities.
Hypochondroplasia
Similar to Achondroplasia, this also develops because of a problem with the conversion of cartilage to bone particularly the long bones of the legs and the arms. The features of this condition appear to be less mild and maybe less noticeable until the child reaches early or middle childhood. Some studies also suggest that the affected children can present mild to moderate intellectual disability.
Diastrophic dysplasia
This is a disorder of the cartilage and bone formation presenting short stature with very short limbs. The affected child may also present early-onset of osteoarthritis and joint deformities called contractures that can restrict normal movements such as walking which can deteriorate with age. Additional features include abnormal curvature of the spine, a cleft palate and deformed ears. Most of the affected individuals can live into adulthood although some of them may experience breathing problems.
Pseudoachondroplasia
This disorder affects the bone growth presenting short stature with an average adult male height as 3 feet 11 inches and the average adult female height as 3 feet, 9 inches. The affected infant may appear normal at birth but by the time they reach age two, their growth rate falls. Additional features include short limbs, osteoarthritis, hyperextensibility which is the abnormal range of movement and the limited rate of motion at the elbows and the hips. The affected individuals present normal facial features and their intelligence remains unaffected.
Spondyloepiphyseal dysplasia congenita
This is an inherited bone growth disorder resulting in a short stature. The features include problems with the bones of the spine and the ends of the long bones of the limbs. In addition, they can also present problems with vision, hearing, a very short trunk and neck although their hands and feet are normal in size. They may also exhibit abnormal curvature of the spine, abnormality of the hip joint, foot deformity (clubfoot), a broad chest and problems with breathing.
References
https://ghr.nlm.nih.gov/condition/achondroplasia
https://ghr.nlm.nih.gov/condition/hypochondroplasia
https://ghr.nlm.nih.gov/condition/diastrophic-dysplasia
https://ghr.nlm.nih.gov/condition/pseudoachondroplasia
https://ghr.nlm.nih.gov/condition/spondyloepiphyseal-dysplasia-congenita
https://www.hon.ch/Dossier/MotherChild/child_musculoskeletal/muscoskel_osteochondrodysplasia.html
