Thanatophoric Dysplasia(TD)
: is the most common form of skeletal dysplasia( severe
skeletal disorder) , lethal in the neonatal period .
Characterized by: extremely short limbs, folds of extra skin on
the arms and legs, a narrow chest, short ribs, underdeveloped lungs, and
an enlarged head with a large forehead and prominent, wide-spaced eyes.
Type I thanatophoric dysplasia: presence of curved
thigh bones and flattened bones of the spine (platyspondyly).
Type II thanatophoric dysplasia: straight thigh bones and a moderate to severe
skull abnormality called a cloverleaf skull.
cause:
Mutations in the FGFR3 gene
(the short-arm of chromosome 4)
FGFR3 gene: encoded Fibroblast
growth factor receptor 3 protein in human. It is involved in the
development and maintenance of bone and brain tissue. Mutations in this gene cause the FGFR3 protein to be
overly active, which leads to the severe disturbances in bone growth that are
characteristic of thanatophoric dysplasia.
FGFR3 protein is part of the tyrosine kinase receptor family. FGFR3 is
a negative regulator of bone growth.
Thanatophoric dysplasia
initiate by sending negative signals to the cartilage cells .These signals
occur when ligand binding within the chondrocytes induces receptor homodimerization
and heterodimerization. As aresult, activation of tyrosine kinase function
potentiates many effects on cell growth and differentiation.
http://emedicine.medscape.com/article/949591-overview#a0104
http://ghr.nlm.nih.gov/condition/thanatophoric-dysplasia
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