Short rib polydactyly syndrome

Incidental findings at second-trimester US screening. Normal NT, standard risk for down syndrome. Non consanguineous-consanguineous couple, no peculiar history.

Important diagnostic landmarks :

Severe shortening of limbs leads to the group of lethal chondrodysplasia, i.e. a chondrodysplasia with narrow thorax severe enough to induce neonatal respiratory distress. Lethal chondrodysplasias are often discovered in the first or second trimester, and consistsconsist of a limited number of disorders.Dominant pattern of narrow thorax, short ribs with polydactyly.Short ribs polydactyly syndrome is part of a spectrum of 4 ciliopathies which includes, for example, Ellis Van-van Creveld (EVC) syndrome and Jeune's asphyxiating thoracic dysplasia.EVC shows the same pattern of short ribs + short limbs + postaxial polydactyly, and cardiac defects are a common feature. However, shortening of limbs are less severe and the prognosis is not lethal.Jeune's syndrome shows also the same pattern of short ribs + short limbs, however, there is usually no postaxial polydactyly and no cardiac defect.  Prognosis is lethal in most cases.All syndromes part ofin this spectrum are inherited (non de novo) in an autosomal recessive fashion. This is important for genetic counselling for the next pregnancy.Important general negative signs, important to describe toin a dominant pattern, which is key to diagnosis and will lead genetic testing:

• -NormalNormal bone density, no fractures (osteogenesis imperfecta in its early and lethal form).
• -NoNo curved limbs ("telephone handset"), especially femur (thanatophoric(thanatophoric dysplasia)
• -NoNo classical widened metaphyses (metatropic dysplasia).
• -NoNo slender, pointy metaphyses, no frontal bossing (achondroplasia (achondroplasia)
• -NoNo hitchhiker thumb (diatrophic dysplasia).
• -NormalNormal clavicles, no widened skull sutures (cleidocranial(cleidocranial dysplasia)
• -NoNo platyspondyly (COL2A spectrum of chondrodysplasia).

Short limbs: biometry is way behind 22WG with a delay greater than 5-6 weeks.Narrow thorax in contrast to the abdomen.Septum membranum VSD.Hyperechoic kidneys.PostaxialPost-axial polydactyly.Polyhydramnios.Fetal ascitis appeared at 33WG.

26 weeks gestation.

Short ribs, short limbs.Negative signs (important for differentials): no trident sign on iliac bones, no platyspondyly.

Feto-pathological exam.Short ribs and narrow thorax, postaxial polydactyly, short limbs.

Widening atypical aspect of metaphyses.

Acetabular roofs are horizontal with an iliac notch called "trident" sign.

PostaxialPost-axial polydactyly involving both feet and hands.