Medical Genetics Inborn errors of metabolism affect about 1 in every 5,000 babies born some of the more familiar born errors of metabolism are cystic fibrosis, hypothyroidism phenylketonuria(PKu) and Tay- Sachs diseaseMedical Genetics Inborn errors of metabolism affect about 1 in every 5,000 babies born. Some of the more familiar inborn errors of metabolism are cystic fibrosis, hypothyroidism,, phenylketonuria (PKU) and Tay￾Sachs disease