TSD is the most lethal, rare, sporadic birth defect due to de novo mutation in the FGFR3 gene.3,4 FGFR3 gene is located in chromosome 4p16.3, responsiblefor givinginstructions for making a protein that is involved in the development and maintenance of bone and brain tissue.4 The malformations due to bone growth seen in TSD are due to overactivation of FGFR3 gene.5 The examination findings, in this case, revealsmacrocephaly, narrow thorax associated with polyhydramnios, micromelia, bowed thigh, frontal bossing, saddle nose, low set ears, protruding abdomen and flattening of the spine. This evidence concerns the gene FGFR3 and Tay-Sachs disease.