Pediatric
Malformation and related entities
Skeletal dysplasias

Author: Erdener Ozer (see Authors page)

Revised: 31 January 2017, last major update January 2017

Copyright: (c) 2017, PathologyOutlines.com, Inc.

PubMed search: pediatric skeletal dysplasias

Cite this page: Skeletal dysplasias. PathologyOutlines.com website. http://pathologyoutlines.com/topic/pediatricskeletaldysplasias.html. Accessed November 23rd, 2017.
Definition / general
Essential features
  • Skeletal dysplasias differ in natural histories, prognoses, inheritance patterns and etiopathogenetic mechanisms
Terminology
  • Osteochondrodysplasias
Epidemiology
  • The prevalence of skeletal dysplasias (excluding limb amputations) is estimated at 2.14 per 10,000 births (Am J Med Genet 1996;61:49)
  • Males are primarily affected in X linked recessive disorders; otherwise, males and females are usually equally affected
Pathophysiology
  • Based on the underlying molecular genetic cause, the dysplasias can be broadly grouped by the function of the protein product of the causative gene
  • Many of the genes mutated in skeletal dysplasias encode proteins that play critical roles in the growth plate
  • Radiographics 2008;28:1061
Etiology
  • FGFR3 gene mutation causes achondroplasia, hypochondroplasia and thanatophoric dysplasia
  • Mutations in the procollagen I genes (COL1A1, COL1A2) cause various types of osteogenesis imperfecta
  • Mutations in the diastrophic dysplasia sulfate transporter gene (DTDST) cause diastrophic dysplasia, achondrogenesis type IB and atelosteogenesis type II
  • Mutations in the procollagen II gene (COL2A1) cause achondrogenesis type II
  • SOX9 gene mutation causes campomelic dysplasia
  • J Back Musculoskelet Rehabil 2015;28:575
Clinical features
  • Typically presents with disproportionate short stature in childhood or premature osteoarthritis in adulthood
  • In addition to the skeletal disorder, individuals frequently demonstrate abnormalities of hearing, vision, neurological, pulmonary, renal or cardiac function
Diagnosis
  • Prenatal evaluation of skeletal dysplasias includes a detailed ultrasound of the fetal skeleton in the second or third trimester of gestation and an extensive genetic family history work up
  • Low dose fetal CT is a powerful imaging tool that aids in diagnosing skeletal dysplasias (Radiographics 2008;28:1061, AJR Am J Roentgenol 2013;200:989)
Radiology description
  • No single unifying features exist; referring to the specific types of skeletal dysplasia for individual features is recommended (World J Radiol 2014;6:808, Radiographics 2008;28:1061)

  • Thanatophoric dysplasia is associated with:
    • Polyhydramnios
    • Thickened soft tissues
    • Micromelia
    • Extremities at 90° to trunk
    • Bowed femur (telephone receiver)
    • Platyspondyly
    • Frontal bossing, depressed nasal bridge
    • Cloverleaf skull (type II)

  • Achondrogenesis is associated with:
    • Polyhydramnios
    • Thickened soft tissues
    • Micromelia
    • Absent ossification of vertebral bodies
    • Normal calvarial ossification (type II)
    • Small thorax, some with rib fractures (type IA)

  • Osteogenesis imperfecta IIA is associated with:
    • Asymmetric micromelia
    • Irregular / thickened bones
    • Angulated bones
    • Beaded ribs, small thorax
    • Poorly ossified skull

  • Osteogenesis imperfecta IIB is associated with:
    • Lower extremities more affected
    • Less beading of ribs
    • Poorly ossified skeleton

  • Osteogenesis imperfecta IIC is associated with:
    • Thin bones, multiple fractures
    • Thin beaded ribs
    • Poorly ossified skull

  • Achondroplasia is associated with:
    • Rhizomelia, mild mesomelia
    • Stubby fingers
    • Frontal bossing
    • Narrowed interpediculate distance
Prognostic factors
  • The prognosis is widely variable, ranging from very mild cosmetic deficits to being lethal
  • Thanatophoric dysplasia and achondrogenesis account for 62% of all lethal skeletal dysplasias
  • Achondroplasia is the most common nonlethal skeletal dysplasia
Treatment
  • Treatment is supportive
  • Mild cosmetic deficits can be treated surgically
Clinical images

Images hosted on other servers:

Thanatophoric dysplasia:
micromelia, platyspondyly, frontal
bossing, depressed nasal bridge,
bowed femur (telephone receiver)

Osteogenesis imperfecta:
Postmortem photograph shows
deformed extremities, findings
that are consistent with fractures

Osteogenesis imperfecta:
Irregular / thickened and
angulated bones, beaded
ribs, small thorax

Microscopic (histologic) images

Images hosted on other servers:

Osteogenesis imperfecta:
area of microfractures

Achondrogenesis: hypercellular
and hypervascular cartilage

Differential diagnosis