TRPS types 1 and 3 are variants of a single disease, type 3 being at the severe end of the clinical spectrum, with very short stature and very severe brachydactyly. They can be distinguished from type 2 trichorhinophalangeal syndrome by the lack of intellectual deficit and exostoses.
TRPS types 1 and 3 are linked to mutations in the TPRS1 gene localised to 8q24.12.
