Thanatophoric dysplasia

Thanatophoric dysplasia (TD) types 1 and 2 may first be suspected during the prenatal period.

During the first trimester of pregnancy, your doctor may notice:

• - shortening of the long bones (femurs and humeri)
• - an increase in the size of the skin fold at the back of the baby's neck, called increased nuchal translucency
• - a reverse in the direction of the blood flow in a specific blood vessel called the ductus venosis

Second and Third Trimester

• - Noticeable growth restriction, particularly of the long bones
• - Broadening of the vertebrae in the spine ("platyspondyly")
• - Increased size of the ventricles (the fluid-filled spaces) in the brain
• - Narrow chest with shortened ribs
• - Low amniotic fluid volume
• - Bowed femurs (TD type I)
• - Enlarged head size
• - Cloverleaf malformation of the skull (frequent in TD type 2, rarely in TD type 1)

After birth, the physician may note the features described above, as well as:

• - Poor overall muscle tone
• - A prominent forehead with a relatively flat face and protruding eyes
• - A larger-than-normal "soft spot" (anterior fontanelle) on the skull
• - A bell-shape of the trunk, with a narrow ribcage and a protruding abdomen
• - Redundant skin folds along the arms and legs
• - Shortened fingers

Performing x-rays (radiographic imaging) is important to help differentiate TD from other types of skeletal dysplasia. Radiologists look for very specific findings to help determine the most likely type of skeletal dysplasia.