Bone
Developmental abnormalities
Achondroplastic dwarfism

Author: Dariusz Borys, M.D. (see Authors page)

Revised: 14 September 2016, last major update June 2012

Copyright: (c) 2003-2016, PathologyOutlines.com, Inc.

PubMed Search: Achondrogenesis
Definition / General
    Type I:
  • Rare, lethal
  • Extreme limb shortening
  • Marked discrepancy between head and trunk size
  • Severely delayed ossification

    Type IA:
  • Autosomal recessive
  • No ossification of vertebral pedicles
  • Rib fractures
  • Chondrocytes have inclusion bodies, but cartilage matrix is near normal

    Type IB:
  • Distinctly abnormal cartilage matrix with rarefaction of ground substance and peculiar ringlike pericellular arrangement of collagen fibers
  • Lethal osteochondrodysplasia due to mutations in transporter gene for diastrophic dysplasia sulfate
  • Genetic defect causes complex derangement in cartilage matrix assembly
  • Impaired decorin deposition causes lack of development of normal interterritorial matrix, preventing necessary structural substrate for proper endochondral bone formation and severe skeletal phenotype
Radiology Images

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Short and abnormal long bones in fetus with type IB

Case Reports
Gross Images

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Achondrogenesis

Micro Description
  • Abnormal endochondral bone formation with curved cartilage-bone junction at growth plates, periosteal bony spurs
  • Spongelike cartilage matrix due to lack of interterritorial matrix
  • Epiphyseal cartilage composed of multiple discrete units of chondrocytes encased in territorial capsule and separated from each other by clefts containing fibroblast like cells
  • Mosaic of chondrocyte units (chondrons) due to breakdown of usual matrix continuity of epiphyseal cartilage
Micro Images

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Abnormal cartilage bone junction, abnormal matrix

Additional References