Diagnosis of short rib polydactyly syndrome type IV (Beemer-Langer syndrome) with cystic hygroma: A case report

Whole exome sequencing, clinical exome or targeted gene panels: what to choose for suspected lethal skeletal dysplasia (short rib thoracic dysplasia type IV)

Lethal skeletal dysplasias (SDs) are a heterogeneous group of rare but important genetic disorders characterised by abnormal growth and development of bone and cartilage. The phenotypic variation of SD highlights the complex aetiology for this group of disorders. Short rib polydactyly syndrome (SRPS) types I-IV are a group of rare congenital autosomal recessive types of SD.We report a case of a non-consanguineous couple whose two successive pregnancies were diagnosed with multiple congenital anomalies in fetuses suggestive of lethal SD (likely SRPS type IV) at 24 and 19 weeks period of gestation, respectively. Pregnancy was terminated, and the whole exome sequencing of the abortus for genetic analysis in the second pregnancy confirmed an autosomal recessive type of short rib thoracic dysplasia-4 (SRTD-4) also called SRPS in homozygous condition. Our case is unique as it was also associated with cystic hygroma which is a rare association with SRPS/SRTD-4.

Autopsy observations in lethal short-rib polydactyly syndromes

The short rib-polydactyly syndromes are a heterogeneous group of lethal autosomal recessive disorders (SRP I-IV), which result from cellular ciliary dysfunction during embryogenesis. Diagnosis is conventionally based on radiographic imaging. Since 1976, postmortem investigations of 5 affected fetuses or stillbirths have been undertaken and the visceral abnormalities have been documented. These anomalies are discussed in the context of prenatal differential diagnosis and prognostication following imaging in pregnancy and at autopsy following miscarriage or stillbirth.

Short rib-polydactyly syndrome type II (Majewski): prenatal diagnosis, perinatal imaging findings and molecular analysis of the NEK1 gene

OBJECTIVE

To demonstrate perinatal imaging findings and to investigate the mutation in the NEK1 gene in a fetus with type II short rib-polydactyly syndrome (SRPS) (Majewski).

CASE REPORT

A 34-year-old woman with a past history of fetal SRPS was referred to the hospital at 16 weeks of gestation because of sonographic diagnosis of short limbs in the fetus. Fetal ultrasound revealed short ribs, short limbs, absence of tibiae, polydactyly, syndactyly and choroid plexus cysts. At 21 weeks of gestation, polycystic kidneys were found. The pregnancy was terminated, and a fetus was delivered with facial dysmorphism, a median cleft lip, a narrow chest, micromelia, aplasia of tibiae, hypoplastic nails, syndactyly and postaxial polydactyly. The karyotype was 46,XX. Molecular analysis of fetal tissues showed a paternal-origin heterozygous splice site mutation in intron 7 (c.465-1 G>A) in the NEK1 gene, but no mutations in the genes of WDR35, DYNC2H1, IFT80, EVC and EVC2. The NEK1 mutation causes an alteration of the splice acceptor site of intron 7 (IVS7-1 G>A). No second mutation was identified.

CONCLUSION

Tibial aplasia, choroid plexus cysts and polycystic kidneys can be prominent prenatal ultrasound findings of type II SRPS. The present case provides evidence for a correlation of NEK1 mutation with type II SRPS.