Year : 2004 | Volume
: 14 | Issue : 2 | Page : 161--163
Antenatal sonography diagnosis of thanatophoric dysplasia : A case report
SV Phatak, MP Pandit, MS Phatak, R Kashikar
Department of Radiodiagnosis, IGMC and Mayo Hospital Nagpur Amarjyoti X-Ray and Sonography Clinic, Wardha Road, Dhantoli-Nagpur-440012, India
S V Phatak
Department of Radiodiagnosis, IGMC and Mayo Hospital Nagpur Amarjyoti X-Ray and Sonography Clinic, Wardha Road, Dhantoli-Nagpur-440012
|How to cite this article:|
Phatak S V, Pandit M P, Phatak M S, Kashikar R. Antenatal sonography diagnosis of thanatophoric dysplasia : A case report.Indian J Radiol Imaging 2004;14:161-163
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Phatak S V, Pandit M P, Phatak M S, Kashikar R. Antenatal sonography diagnosis of thanatophoric dysplasia : A case report. Indian J Radiol Imaging [serial online] 2004 [cited 2019 Dec 13 ];14:161-163
Available from: http://www.ijri.org/text.asp?2004/14/2/161/28576
Thanatophoric dwarfism is characterized by severe Micromelic limb shortening, bowing of limbs, narrowed thorax, severe platyspondyly , Polyhydramnios (71% of cases) cloverleaf skull 14% of cases ) and a small pelvis are also associated conditions .
A forty year lady with previous three normal children was referred for Sonography to rule out twins as uterine fundal height was more than expected gestational age of 30 weeks. Ultrasound revealed severe polyhydramnios. Biparietal diameter and abdominal circumference was corresponding to 30 weeks. Fetal femur, humerus, radius, ulna, tibia and fibula length was corresponding to 15-16 wks. Fetal chest was narrow and ribs were short. Fetal femur and humerus showed bowing. On the basis of severe micromelia, bowing of humerus and femur, narrow chest and short ribs accompanied by severe polyhydramnios possibility of lethal dwarfism syndrome of Thanatophoric dysplasia was suggested. Patient opted for termination of pregnancy. Photographs and radiographs of fetus were taken. Radiograph showed severe micromelia with bowing prominently seen in femur and humerus (telephone receiver deformity) with excessive soft tissue. Fingers were short and stubby, narrow thorax, severe platyspondyly and small pelvis. Metaphysis of long bones showed irregularity and cupping.
On Sonography following long bone measurement it is possible to determine which part of the limb is more severely shortened using graphs published by Romero et al. The dysplasias may then be divided into following broad categories . Rhizomelic dysplasia:- Shortening of proximal portion of limb out of proportion to the middle portion of the limb.
Mesomelic dysplasia:- Shortening of middle portion of limb out of proportion to proximal portion of limb.
Micromelic dysplasia :- Shortening of proximal and middle portion of limb.
Spirt et al further subdivide Micromelic dysplasia into mild micromelia, mild and bowed micromelia and severe micromelia .
Severe micromelia is seen with most of the lethal dysplasias represented most commonly by Thanatophoric dysplasia.
If polyhydramnios is present with dwarfing syndrome the bone dysplasia is almost certain to be lethal. The polyhydramnios is thought to be due to compression of esophagus by the small chest seen with most dwarfism syndromes the abdomen balloons out in bell shaped fashion below the rib cage .
The basic pathogenetic mechanism proposed for Thanatophoric dysplasia is persistence of abnormal fetal mesenchymal tissue leading to disorganized enchondral bone formation, which transforms to abnormal bone and cartilage .
The genetic aetiology is now recognized to be a dominant new gene mutation in extra cellular region of fibroblast growth factor receptor 3 gene also called FGFR 3 gene  Cohen believes that hypochondroplasia, achondroplasia and Thanatophoric dysplasias are different ends of the FGFR 3 mutation with hypochondroplasia being mildest and Thanatophoric dysplasia the most severe form .
Radiographic features :- There is severe micromelia with bowing of extremities; skull has a large base and prominent frontal bone. Chest is narrow and ribs are short. There is reduction of interpediculate spaces of last few lumbar vertebrae. The iliac wings are small and square, the sacrosciatic notch is narrow and acetabular roof horizontal. All these changes are similar to those seen in Achondroplasia. The feature distinguishing Thanatophoric dwarfism from Achondroplasia are severe vertebral plana and excessive intervertebral space height. Short tubular bones are bowed; the metaphyseal areas are irregular and frequently cupped..
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