TBX4 and coxopodopatellar syndrome: The importance of the TBX4 gene in the developmental pathways of the lower limbs and the pelvis in humans were established based on the identification of heterozygous TBX4 mutations in small patella syndrome (SPS; OMIM 147891) patients, and the observation of similar skeletal phenotype on animals lacking Tbx4 gene [6,7].