Short rib polydactyly syndrome (without polydactyly)

Case contributed by Dr Fabien Ho

Presentation

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

Patient Data

Age: 23 weeks gestation
Gender: Male

US from 23 to 27WG

Ultrasound

Narrow thorax in contrast to the abdomen. Short limbs: biometry delayed, greater than 5-6 weeks from expected 23WG.

Normal clavicle and normal skull. Normal face, normal heart (not shown), normal kidneys, no polydactyly.
 

Fetal growth chart

Annotated image

All limbs growth are way below expected length with a significant delay, contrasting with preserved skull biometrics.

Fetal bone CT at 24WG

CT

Short ribs, short limbs. Illiac bone trident sign can be seen. Normal skull and clavicles.

post mortem xray at 37WG

X-ray

Short ribs and narrow thorax, short limbs. Acetabular roofs are horizontal with an iliac notch called "trident" sign.Widening atypical aspect of metaphyses, almost "banana-peeled" shape.

Case Discussion

This pattern of a narrow thorax, short bones, trident-shaped acetabular roof, severe enough to be lethal after delivery led to the diagnosis of short rib polydactyly syndrome (without polydactyly) in its most common subtype, type III Verma Vaumoff with banana peel shaped metaphyses.

This companion case (rID: 57784) demonstrates features of the same diagnosis but with a slightly more severe pattern and with polydactyly.

Short-rib thoracic dysplasia (SRTD) with or without polydactyly refers to a group of autosomal recessive skeletal ciliopathies that are characterized by a constricted thoracic cage, short ribs, shortened tubular bones, and a 'trident' appearance of the acetabular roof.

Polydactyly is variably present, and there is phenotypic overlap in the various forms of SRTDs, which differ by visceral malformation and metaphyseal appearance. Nonskeletal involvement can include cleft lip/palate as well as anomalies of major organs such as the brain, eye, heart, kidneys, liver, pancreas, intestines, and genitalia. Some forms of SRTD are lethal in the neonatal period due to respiratory insufficiency secondary to a severely restricted thoracic cage, whereas others are compatible with life.

SRTD encompasses:

  • short rib polydactyly syndrome (SRPS), perinatally lethal which has four different subtypes:
    • type I Saldino-Noonan (rare) long bones with a torpedo-shape appearance
    • type III Verma-Naumoff type (most common) which has a banana-peel shape
    • type II Majewski: characteristically short, oval tibia
    • type IV Beemer: resembles the Majewski syndrome to a certain extent, but the tibiae are not as short and polydactyly is rarely present
  • asphyxiating thoracic dystrophy (Jeune syndrome): potentially surviving and mild
  • chondroectodermal dysplasia (Ellis–van Creveld syndrome): acromelic and mesomelic limb shortening with smooth rounded metaphyses, postaxial polydactyly, small chest, ectodermal dysplasia, and, in many cases, congenital heart defects

Dr F Cuillier, Dr M Balu and Dr J-L Alessandri also significantly contributed to this case.

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