Trichorhinophalangeal syndrome, type I (TRPS I)

TRPS1 related disorders

Trichorhinophalangeal syndrome type I (TRPS I; MIM 190350) and type III (TRPS III; MIM 190351) are allelic autosomal dominant disorders characterized by craniofacial and skeletal abnormalities. TRPS is characterized by slow growing, sparse scalp hair, laterally sparse eyebrows, a pear shaped nose with a bulbous tip, a long flat philtrum, a thin upper vermillion border, protruding ears, and postnatal, progressive growth retardation. Skeletal abnormalities include cone shaped epiphyses of the phalanges and other bones, shortening of the phalanges and metacarpals, hip malformations and short stature. The skeletal age lags behind the chronological age until puberty. Patients with TRPS III are more severely affected than those with TRPS I and are typically shorter and have more severe brachydactyly involving all tubular bones of the hands. They may also have additional skeletal abnormalities. TRPS I and TRPS III are caused by mutations in the zinc-finger transcription factor gene, TRPS1. TRPS1 haploinsufficiency is considered the major cause of TRPS I. TRPS III is typically caused by mutations resulting in substitutions in a specific DNA binding domain. It is proposed that these mutations exert a dominant negative effect.
Trichorhinophalangeal syndrome, type II (TRPS II) shares many clinical features with TRPS I and TRPS III; however, patients with TRPS II have multiple cartilaginous exostoses, mental retardation, and some may have microcephaly. TRPS II is a contiguous gene syndrome caused by the deletion of the TRPS1 and EXT1 genes.