Thanatophoric dysplasia type 2

The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.

Thanatophoric dysplasia, type 2 (TD2) is a form of TD (see this term) characterized by micromelia, straight long-bones, macrocephaly, brachydactyly, shortened ribs and a clover-leaf skull (kleeblattschaedel).

The prevalence is unknown but it is less common than TD1 (see this term).

TD2 presents in the prenatal period (in the first to second trimester) with micromelia, long-bones (femurs) that are straight and not as short as those seen in TD type 1, platyspondyly of the vertebrae, narrow thorax, and a cloverleaf (trilobed) skull. Distinctive facial features include macrocephaly, frontal bossing, low nasal bridge, large anterior fontanel and proptosis. Polyhydramnios is common. Neonates usually die shortly after birth due to respiratory insufficiency and/or spinal cord/brain stem compression.

TD2 is caused by a single missense mutation (K650E) in the fibroblast growth factor receptor 3 (FGFR3) gene, located to chromosome 4p16.3.

TD2 is inherited autosomal dominantly but the majority of cases are due to a de novo mutation in the proband. Genetic counseling allows families who have already had one child with TD2 to know that recurrence rate is about 2%, so their chance of having a healthy child is high. Expert reviewers: Dr. Michael Bober and Ms. Angie Duker

Visit the Orphanet disease page for more resources.

Last updated: 10/1/2013

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