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1999-06-17-19 Short rib-polydactyly syndrome © Silva www.thefetus.net/


Short rib polydactyly syndromes

Sandra R Silva, MD & Philippe Jeanty, MD, PhD

Definition: Short rib polydactyly syndromes are lethal forms of skeletal dysplasia, characterized by thoracic hypoplasia, polydactyly and shortening of the long bones. Three types of the disorder were described:

·         Type I: described by Saldino and Noonan in 1972[1];

·         Type II: described by Majewski in 1971[2];

·         Type III: described by Naumoff in 1977[3].
Clinical, radiographic and morphologic studies suggest that types I and III just represent phenotypic variations of the same disorder.

Incidence: Because of the rarity of the condition, the incidence is not precisely known. No sex preference has been observed[4].

Etiology: The disorder has an autossomal recessive transmission, and thus the recurrence risk is 25%4.

Diagnosis: Prenatal diagnosis by ultrasound can be accomplished by finding the characteristic triad which includes micromelic dwarfism, short and horizontal ribs with narrow thorax (what leads to hypoplasia of the lungs), and polydactyly.

Some typical features, more frequently seen after birth, differentiate type I from type II: Type I (Saldino-Noonan): short stature, postaxial polydactyly of hands and/or feet, syndactyly, underossified phalanges, notch-like ossification defect of vertebral bodies, small iliac bones, triangular ossification defects above the acetabulum. Cardiac, gastrointestinal, and urogenital malformations can also be found. Occasionally preaxial polydactyly and sex-reversal (46,XY with female phenotype) can occur[5].

Type II (Majewski): short stature with extremely short limbs, midline cleft lip, cleft palate, short flat nose, low set and malformed ears, preaxial and postaxial polysyndactyly of hands and feet, premature ossification of proximal epiphyses of femur, humerus and lateral cuboids, underossified phalanges, high clavicles, and ambiguous genitalia. Less frequently, hydrops and polyhydramnios can also be found[6]. 

Genetic anomalies: Probable gene anomaly either 4q13 or 4p16.

Differential diagnosis: The differential diagnosis includes all skeletal dysplasias associated with micromelia and short ribs such as: thanatophoric dwarfism, chondrodysplasia punctata, osteogenesis imperfecta, and camptomelic dysplasia[7]. Oro-facial-digital syndrome type II is another differential diagnosis of the Majewski type6. Most of these conditions are excluded only after birth, by radiographic and morphologic studies.

Prognosis: SPRS are lethal conditions. Affected neonates usually die few hours after birth from respiratory insufficiency, due to severe pulmonary hypoplasia5, 6.  

Management: Termination of pregnancy can be offered before viability. Standard prenatal care is not changed when continuing the pregnancy is opted. Confirmation of diagnosis after birth is important for genetic counseling.

Reference:

[1] Saldino RM, Noonan CD (1972): Sever thoracic dystrophy with striking micromelia, abnormal osseous development, including the spine, and multiple visceral anomalies. Am J Roentgenol 114: 257-263.

[2] Majewski F, Pfeiffer RA, Lenz W, Muller R, Feil G, Seiler R (1971): Polydactyly, short limbs, and genital malformations - a new syndrome? Z Kinderheilkd 111: 118-138.

[3] Naumoff P, Young LW, Maser J, Amortegui AJ (1977): Short rib polydactyly syndrome type 3. Radiology 122: 443-447.

[4] Meng HW, Pao LK, Shio JL (1995): Prenatal diagnosis of recurrence of short rib polydactyly syndrome. Am J Med Genet 55: 279-284.

[5] Jones KL (1997): Short rib polydactyly syndrome type I ( Saldino-Noonan type) in Smith"s Recognizable Patterns of Human Malformation - 5th Edition - WB Saunders Company - Philadelphia.

[6] Jones KL (1997): Short rib polydactyly syndrome type II ( Majewski type) in Smith"s Recognizable Patterns of Human Malformation - 5th Edition - WB Saunders Company - Philadelphia.

[7] Gembruch U, Hansmann M, Fodisch HJ (1985): Early prenatal diagnosis of short rib polydactyly (SRP) syndrome  type I (Majewski) by ultrasound in a case at risk. Prenat Diagn 5: 357-362.

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