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achondrogenesis type 2

MIM.200610 12q13.11-q13.2

Friday 19 January 2007

Definition: Autosomal dominant chondrodyplasia.

The mutations are present in heterozygous state in the affected infants, and are always de novo, indicating that they represent new dominant mutations. This disorder was previously cataloged (incorrectly, as it turned out) as an autosomal recessive.

Mutations have been identified in the COL2A1 gene (MIM.120140). The mutations are heterozygous in affected infants, and are always de novo, indicating that they represent new dominant mutations.

Macroscopical synopsis

- large head
- short trunk
- severe micromelia
- no ossification of vertebra, ischial and pubic bones
- severe micromelic dwarfism
- cleft palate
- cystic hygroma
- barrel-shaped chest
- short trunk
- short ribs
- horizontal ribs
- normal clavicles
- distended abdomen
- enlarged calvaria with normal ossification
- absent vertebral body mineralization
- non-ossified sacrum, ischial, and pubic bones
- small iliac wings with concave inferior and medial margin
- very short and broad tubular bones
- flared, cupped metaphyses
- short tubular bones
- non-ossified talus and calcaneus
- short tubular bones
- fetal hydrops
- polyhydramnios
- stillborn or neonatatl death

Microscopical synopsis

- retsing cartilage

  • severe generalized deficiency of the matrix (very scant matrix)
  • increased number of markedly enlarged lacunae and chondrocytes that may have abundant clear cytoplasm
  • large and stellate cartilage canals
  • markedly enlarged cartilage canals
  • stellate in shape cartilage canals
  • fibrotic cartilage canals

- physeal growth plate

  • poorly defined physeal growth plate
  • markedly retarded physeal growth plate
  • disorganized physeal growth plate
  • closely arranged large chondrocytic lacunae
  • prominently deficient intervening matrix

- predominant collagen is type 1 rather than type 2 (disorder of type 2 collagen biosynthesis by COL2A1 germline mutations)

Case records

- Case 10610: Achondrogenesis type 2

See also

- achondrogeneses

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