Osteochondrodystrophy

Synonym: skeletal dysplasia

Heterogeneous group of more than 200 disorders characterised by abnormalities of cartilage and bone growth resulting in abnormal shape and size of the skeleton and disproportion of the long bones, spine, and head. Conditions include:

• Usually fatal: achondrogenesis, thanatophoric dysplasia, short rib polydactyly (Majewski and Saldino-Noonan type), homozygous achondroplasia, osteopetrosis (congenital), camptomelic dysplasia, dyssegmental dysplasia (Silverman-Handmaker type), osteogenesis imperfecta type II, hypophosphatasia (congenital), chondrodysplasia (rhizomelic)
• Often fatal: asphyxiating thoracic dystrophy (Jeune syndrome)
• Occasionally fatal: Ellis-van Creveld syndrome, diastrophic dysplasia, metatropic dwarfism, Kniest dysplasia

• Incidence is in the region of 1/4,000 births.¹
• Lethal skeletal dysplasias are estimated to occur in 0.95 per 10,000 deliveries.
• The 4 most common skeletal dysplasias are thanatophoric dysplasia, achondroplasia, osteogenesis imperfecta, and achondrogenesis.
• Thanatophoric dysplasia and achondrogenesis account for 62% of all lethal skeletal dysplasias. Achondroplasia is the most common non-lethal skeletal dysplasia.
• Maternal usage of warfarin or phenytoin may induce stippling of the epiphyses, resembling chondrodysplasia punctata.

• Skeletal dysplasias are usually evident in the newborn period or during infancy but some disorders do not present until later in childhood.
• Disproportionate short limbs should be considered if arms do not reach the mid pelvis in infancy or upper thigh later.
• Maternal hydramnios is probably the most significant event associated with fetal skeletal dysplasia during pregnancy.

• Features include:
• Disproportionately short stature (short limbs or short trunk)
• Disproportionate shortening may be:
  • Short proximal segments - humerus, femur: e.g. achondroplasia, hypochondroplasia, spondyloepiphyseal dysplasia congenita, diastrophic dysplasia, and congenital short femur
  • Short middle segments - radius, ulna, tibia, fibula: e.g. Langer and Nievergelt types of mesomelic dysplasias, Robinow syndrome, Reinhardt syndrome
  • Short distal segments - metacarpals, phalanges: e.g. acrodysostosis and peripheral dysostosis
  • Short middle and distal segments - forearms, hands, e.g. acromesomelic dysplasia
  • Shortening of extremities involving entire limb: e.g. achondrogenesis, fibrochondrogenesis, dys-segmental dysplasia, Roberts syndrome
  • Short trunk (short neck, small chest and protruding abdomen): e.g. Morquio's syndrome, metatrophic dysplasia, spondyloepimetaphyseal dysplasia
• Other features may include:
  • Delayed motor milestones
  • Airway obstruction
  • Pain, deformity and neurological deficits caused by spinal disorders
• Other skeletal anomalies include large head with hydrocephalus, bowlegs with waddling gaits.
• There are different neurological, cardiovascular and many other specific abnormalities associated with specific osteochondrodystrophies.

• If short stature is proportional, the condition may be due to endocrine or metabolic disorders, or chromosomal or non-skeletal dysplasia genetic defects.
• In general, patients with disproportionately short stature have osteochondrodysplasia.

• Skeletal survey to assess the whole dysplastic skeleton.
• Various biochemical, haematological and immune function tests depending on the osteochondrodysplasia and individual patient context.
• Further assessments will include ultrasound, CT and/or MRI scan, echocardiogram.
• Molecular studies and cytogenetic studies.

• Babies with certain disorders diagnosed antenatally, such as achondroplasia, should be delivered by caesarean section.
• Treatment is symptomatic, including orthopaedic interventions such as spinal fusion, bone lengthening and also use of a brace, e.g. for kyphosis.
• Bone marrow transplantation may benefit patients with skeletal dysplasia associated with congenital immune deficiencies, mucopolysaccharidosis, lipidosis, osteopetrosis, and Gaucher's disease.

• Prognosis depends on precise nature of the specific osteochondrodysplasia.
• Among infants with skeletal dysplasias detected at birth, approximately 13% are stillborn and 44% die during the perinatal period.
• Overall frequency of skeletal dysplasias in infants who die perinatally is 9.1 per 1000.