Morgan Stephen,  Conway Deborah

Final Pr. ID: Poster #: CR-008

An infant was born at 36 weeks, 3 days gestation with a known lethal skeletal dysplasia, diagnosed on prenatal ultrasound. The infant was born alive with APGARs of 5 and 3. Comfort care was initiated, and the infant expired one hour later. Plain films of the skeletal system were obtained, which showed short, horizontal ribs and a small thorax. They also showed hypoplastic iliac bones, flattened acetabula, and postaxial polydactyly. The metaphyses of the long bones had convex central areas with lateral metaphyseal spikes. The constellation of findings was consistent with Short Rib Polydactyly Syndrome type III (Verma-Naumoff).

Inherited in an autosomal recessive pattern, SRPS is a group of rare, lethal osteochondrodysplasias caused by mutations in the DYNC2H1 gene, a component of the cytoplasmic dynein complex, which is involved in the generation and maintenance of cilia. This mutation results in dyskinesia involving the chondrocytes, leading to arrested maturation of cartilage and generalized loss of synchrony in cartilage removal and osteogenic differentiation.

Common anomalies that span all types of SRPS include a triad of micromelia, short horizontal ribs, and polydactyly. Four types of short-rib polydactyly syndrome have been described, which differ based on visceral involvement and the appearance of the metaphyses. Some have phenotypic overlap with various types of Short Rib-Thoracic Dysplasia. The four types of SRPS are: Saldino-Noonan (type I), Majewski (type II), Verma-Naumoff (type III), and Beemer-Langer (type IV). Type I (SN) is characterized by hypoplastic iliac bones, flattened acetabular roofs, rounded vertebrae with coronal clefts, and postaxial polydactyly. The long bones can have varied appearance of the metaphysis, including: pointed ends, convex central areas with lateral metaphyseal spikes, or ragged-appearing ends. A key distinguishing factor with type I is the absence of fibulae. Type III (VN) is very similar to type I, however, the fibulae are present. Visceral anomalies are less common with the Verma-Naumoff type. Type II (Majewski) presents with either pre- or postaxial polydactyly. The long bone metaphyses have smooth ends, the tibiae are ovoid and shorter than the fibulae, and the iliac bones are normal. Type IV (BL), like type II, can also have pre- or postaxial polydactyly and smooth metaphyses in the long bones. The distinguishing characteristics of the Beemer-Langer type include small iliac bones and bowed radii/ulnae. Read More

Authors:  Morgan Stephen , Conway Deborah

Keywords:  Short Rib Polydactyly Syndrome, Verma-Naumoff, osteochondrodysplasia