Thanatophoric dysplasia
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Thanatophoric dysplasia (TD) is a lethal skeletal dysplasia. It is the 2nd most commonest lethal skeletal dysplasia after osteogenesis imperfecta type II.
Epidemiology
The estimated incidence is at around 1: 25:25,000-50,000 3.
Pathology
Genetics
It results from a mutation coding for the fibroblast growth receptor 3(FGFR3) located in chromosome 4p16.3. The type of receptor mutation is different from the FGFR mutation in achondroplasia. Inheritance is thought to be sporadic.
Sub types
There are two recognised sub types.
-
type I:
: markedmarked under development of skeleton, telephone handle femurs more pronounced. -
type II:
:- the presence of a cloverleaf skull may be a distinctive feature
- limb shortening milder and bowing is not a feature 3
Associations
Radiographic features
Antenatal ultrasound
It may be difficult to accurately diagnose before the 3rd trimester ( ≈ 22≈22 weeks) 4. Prior to that time it can be in included in the differential if there is a short femur length measurement.
Sonographically detectable features may include:
- relatively narrow thoracic cavity 4
- short, thick, bowed tubular bones, especially lower extremity 4
- thickened soft tissues of extremities 4
- comparatively large head with frontal bossing
- a cloverleaf skull appearance may also be seen -type II (see case 3)
Plain film
Plain films if done at all are usually done post mortem. Features include:
Limbs
- proximal portions of the long limbs are small giving a rhizomelic appearance.
- long limbs (typically humeri and femora) have a typical "telephone handle" bowing with metaphyseal flaring.
Iliac bones
- usually hypoplastic
- small squared iliac wings
- may show a "trident" acetabular roof
Chest
- narrow chest
- short horizontal ribs
- small scapulae
Skull and face
- relative macrocephaly
- frontal bossing
- proptosis
- nasal bridge flattening
- Kleeblattschaedel, or cloverleafskull (with type II)2-4
Spine
- platyspondyly: flattening of vertebral bodies
- normal trunk length
EtymologyHistorical context
The term thanatophoric derives from the Greek word "thanatos"thanatos - θάνατος" meaning bearing death 2.
Prognosis
The condition is uniformly fatal within a few hours of birth either from respiratory failure or from brainstem compression from a narrow foramen magnum.
See also
-<p><strong>Thanatophoric dysplasia (TD)</strong> is a <a href="/articles/lethal-skeletal-dysplasias">lethal skeletal dysplasia</a>. It is the 2<sup>nd</sup> most commonest lethal skeletal dysplasia after <a href="/articles/osteogenesis-imperfecta-1">osteogenesis imperfecta</a> type II. </p><h4><strong>Epidemiology</strong></h4><p>The estimated incidence is at around 1: 25,000-50,000 <sup>3</sup>.</p><h4><strong>Pathology</strong></h4><h5>Genetics</h5><p>It results from a mutation coding for the fibroblast growth receptor 3(FGFR3) located in chromosome 4p16.3. The type of receptor mutation is different from the FGFR mutation in <a href="/articles/achondroplasia">achondroplasia. </a>Inheritance is thought to be sporadic.</p><h5>Sub types</h5><p>There are two recognised sub types.</p><ul>- +<p><strong>Thanatophoric dysplasia (TD)</strong> is a <a href="/articles/lethal-skeletal-dysplasias">lethal skeletal dysplasia</a>. It is the 2<sup>nd</sup> most commonest lethal skeletal dysplasia after <a href="/articles/osteogenesis-imperfecta-1">osteogenesis imperfecta</a> type II. </p><h4><strong>Epidemiology</strong></h4><p>The estimated incidence is at around 1:25,000-50,000 <sup>3</sup>.</p><h4><strong>Pathology</strong></h4><h5>Genetics</h5><p>It results from a mutation coding for the fibroblast growth receptor 3 (FGFR3) located in chromosome 4p16.3. The type of receptor mutation is different from the FGFR mutation in <a href="/articles/achondroplasia">achondroplasia</a>. Inheritance is thought to be sporadic.</p><h5>Sub types</h5><p>There are two recognised sub types.</p><ul>
-<strong>type I</strong>: marked under development of skeleton, telephone handle femurs more pronounced.</li>- +<strong>type I:</strong> marked under development of skeleton, telephone handle femurs more pronounced.</li>
-<strong>type II</strong>:<ul>- +<strong>type II:</strong><ul>
-</li></ul><h4><strong>Radiographic features</strong></h4><h5>Antenatal ultrasound</h5><p>It may be difficult to accurately diagnose before the 3<sup>rd</sup> trimester ( ≈ 22 weeks) <sup>4</sup>. Prior to that time it can be in included in the differential if there is a short femur length measurement. </p><p>Sonographically detectable features may include</p><ul>- +</li></ul><h4><strong>Radiographic features</strong></h4><h5>Antenatal ultrasound</h5><p>It may be difficult to accurately diagnose before the 3<sup>rd</sup> trimester (≈22 weeks) <sup>4</sup>. Prior to that time it can be in included in the differential if there is a short femur length measurement. </p><p>Sonographically detectable features may include:</p><ul>
-</ul><h5>Plain film </h5><p>Plain films if done at all are usually done post mortem. Features include</p><h6><strong>Limbs</strong></h6><ul>- +</ul><h5>Plain film </h5><p>Plain films if done at all are usually done post mortem. Features include:</p><h6><strong>Limbs</strong></h6><ul>
-<a href="/articles/cloverleaf-skull">Kleeblattschaedel</a>, or <a href="/articles/cloverleaf-skull">cloverleaf</a><a href="/articles/cloverleaf-skull"> </a><a href="/articles/cloverleaf-skull">skull </a>(with type II)<a href="/articles/cloverleaf-skull-"> </a><sup>2-4</sup> </li>- +<a href="/articles/cloverleaf-skull">Kleeblattschaedel</a>, or <a href="/articles/cloverleaf-skull">cloverleaf</a><a href="/articles/cloverleaf-skull"> </a><a href="/articles/cloverleaf-skull">skull </a>(with type II) <sup>2-4</sup> </li>
-</ul><h4>Etymology</h4><p>The term <strong>thanatophoric</strong> derives from the Greek word "<strong>thanatos - θάνατος</strong>" meaning bearing death <sup>2</sup>.</p><h4>Prognosis</h4><p>The condition is uniformly fatal within a few hours of birth either from respiratory failure or from brainstem compression from a narrow foramen magnum.</p><h4>See also</h4><ul><li><a href="/articles/skeletal-dysplasia">skeletal dysplasias</a></li></ul>- +</ul><h4>Historical context</h4><p>The term thanatophoric derives from the Greek word "thanatos - θάνατος" meaning bearing death <sup>2</sup>.</p><h4>Prognosis</h4><p>The condition is uniformly fatal within a few hours of birth either from respiratory failure or from brainstem compression from a narrow foramen magnum.</p><h4>See also</h4><ul><li><a href="/articles/skeletal-dysplasia">skeletal dysplasias</a></li></ul>
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