Short rib – polydactyly I, II, III, IV

Short rib – polydactyly I, II, III, IV


The short rib-polydactyly syndromes (SRPS) consist of micromelia, polydactyly and severe rib shortening. The SRPS are classified into types I, ll, lll and IV, although some authors recognize up to 7 types. All are inherited in autosomal recessive fashion and are lethal. Synonyms include: SRP syndromes I-IV; Saldino-Noonan (SRP-I); Majewski (SRP-II); Verma-Naumoff (SRP-III); Beemer-Langer (SRP-IV)


It has been suggested that SRPS types I,III and types II,IV represent variability in the same disorder. However, they all present with a short, narrow thorax, a protuberant abdomen, severely shortened horizontal ribs, micromelia, polydactyly and brachydactyly. SRPS type I also has a dolichocephalic head, micrognathia, small scapulae and hypoplastic iliac bones. The tubular bones have ragged ends, there are metaphyseal spurs, the fibula is absent and the femurs are pointed. In SRPS type II there is a prominent forehead, cleft lip and palate and an underdeveloped mandible. The metaphyses are rounded. The tibia is extremely short and ovoid in configuration, with an overdeveloped fibula by comparison. There is precocious ossification of the proximal femoral epiphysis. SRPS type III is similar to type I, but less severe. There is a bulging forehead, cleft lip and palate and hypoplastic, thin vertebrae. The metaphyses are rounded with lateral spikes. The tibia and fibula are similarly developed. Polydactyly may or may not be present. SRPS type IV is similar to type II with the exception of no polydactyly and a more normally developed tibia. All SRPS frequently have associated anomalies of the internal organs and external genitalia. The ratio of rib cage perimeter to thoracic circumference may prove useful in diagnosis. This ratio is independent of gestational age, the mean in a normal pregnancy being 0.67 +/- 0.004. In a small series the ratio was decreased in fetuses with skeletal dysplasias, particularly so in the case of short rib-polydactyly. The diagnosis is reported as being made in the 2nd trimester.

Differential Diagnosis

Achondrogenesis may be differentiated by the abnormal spine and/or skull ossification, longer ribs and absence of polydactyly. In homozygous achondroplasia both parents will be affected. Asphyxiating thoracic dysplasia has less severe shortening of ribs and long bones, polydactyly is seldom seen. Atelosteogenesis type II features hitchhiker thumbs, a horizontal sacrum, longer ribs and no polydactyly. In chondroectodermal dysplasia (Ellis-van Creveld syndrome) the ribs are slightly shortened and there is mild rhizomelic long bone compromise. Fibrochondrogenesis has an undermineralized skull, coronal clefts, longer ribs and no polydactyly. Osteogenesis imperfecta type II has multiple fractures and, frequently, abnormal calvarial ossification; the ribs are of normal length and there is no polydactyly. Schneckenbecken dysplasia has longer ribs, no polydactyly and the posterior aspect of the vertebral body is missing. In thanatophoric dysplasia the ribs are longer and there is no polydactyly.

Sonographic Features

Short and narrow thorax

Severe rib shortening

Horizontal ribs


Femoral metaphyses: pointed (SRP-I); rounded (SRP-II); rounded with lateral spikes (SRP-III)


Absent fibula (SRP-I)

Ovoid tibia, shorter than fibula (SRP-II)

Tibia and fibula of similar length (SRP-III)

Proximal femoral ossification centre (SRP-II)

Cleft lip/palate (SRP-II&III)

Genital anomalies

Associated Syndromes 


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