Thanatophoric dwarfism

Case contributed by Mr. Dennis Odhiambo Agolah

Presentation

Thirty years old female gravida two. Thirty weeks gestation presenting with reduced fetal movements sent for an ultrasound to rule out polyhydramnios.

Patient Data

Age: 30 weeks gestation
Gender: Female
Ultrasound

Symmetrically foreshortened (micromelic) bilateral upper and lower fetal limbs with subtly bowed left tibial and femoral shafts (camptomelic).

The fetal feet are medially rotated consistent with bilateral Talipes equinovarus (CTEV). The fetal spinal column is mildly flattened.

The fetal chest collumn is foreshortened (primarily due to short ribs) with resultant fetal abdominal protruberance.

The fetal head circumference is relatively larger compared with rest of the biometric parameters pointing towards macrocephaly however, no features of hydrocephalus or intra-cranial space occupying lesions.

Marked polyhydramnios (amniotic fluid index= 28.58 cm) with the mentioned liquor displaying densely speckled diffuse internal echoes likely attributed to an infective process. No other gross fetal anomalies.

Case Discussion

Present, but markedly foreshortened fetal upper and lower extremities with a stark discordance in the respective biometric parameters with the femur lengths lagging at 20 weeks while the rest of the biometrics ranging from 30+ weeks. The arms and legs demonstrates redundant and thickened skin folds.

An apparent fetal frontal head bossing, narrowed and foreshortened chest (with underdeveloped fetal lungs), the mildly prominent and spaced orbits plus the aforementioned redundant limbs noted, are consistent with thanatophoric dwarfism.

Thanatophoric dwarfism (a.k.a thanatophoric dysplasia or osteochondroplasia or skeletal dysplasia) is a lethal skeletal disorder presenting with short limbs and redundancy of the skin folds. Two major types are described: Type I and II. In type I thanatophoric dysplasia, fetal thigh bones are curved and the spinal vertebral bones are flattened (platyspondyly). In type II, the femoral bones are straight but the fetal skull shows cloverleaf appearance. Both types I and II results from abnormal mutations of FGFR3 gene that leads in the gene's proteins being overly active thus leading to severe disturbances in bone growth1,2,3,4.

In this series, features of bilateral congenital talipes equinovarus (CTEV) and chorioamnionitis in the setting of polyhydramnios are also evident.

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