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Bone

Developmental abnormalities

Achondrogenesis


Reviewers: Dariusz Borys, M.D. (see Reviewers page)
Revised: 1 June 2012, last major update June 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
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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

Radiologic images
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Short and abnormal long bones in fetus with type IB

Case reports
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● Child with consanguineous (first cousins) parents and type IB (Arch Pathol Lab Med 2001;125:1375)

Gross images
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Achondrogenesis

Micro description
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● 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
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Achondrogenesis

End of Bone > Developmental abnormalities > Achondrogenesis


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