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Gene: TTC21B

Green List (high evidence)

Short-rib thoracic dysplasia (SRTD) with or without polydactyly is a skeletal ciliopathy characterized by a constricted thoracic cage, short ribs, shortened tubular bones, and a 'trident' appearance of the acetabular roof. SRTD encompasses Ellis-van Creveld syndrome (EVC) and the disorders previously designated as Jeune syndrome or asphyxiating thoracic dystrophy (ATD), short rib-polydactyly syndrome (SRPS), and Mainzer-Saldino syndrome (MZSDS). Polydactyly is variably present. Nonskeletal involvement can include cleft lip/palate as well as anomalies of 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.
Homozygous null alleles in Ttc21b are embryonic lethal in mice and it is likely that biallelic truncating null variants are equally incompatible with survival in humans.

Created: 22 Jan 2025, 3:58 a.m. | Last Modified: 22 Jan 2025, 3:58 a.m.

Panel Version: 1.1257

Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal

Phenotypes
Short-rib thoracic dysplasia 4 with or without polydactyly, MIM #613819

Publications

• PMID: 21258341
• 25492405
• 33875766