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