Hereditary and Congenital Diseases
Hereditary diseases such as hemophilia , sickle-cell anemia , Huntington's disease , muscular dystrophy , and Tay-Sachs disease are caused by mutated genes inherited from one or both parents (see Genetic Disorders ). Certain other diseases, such as diabetes mellitus , hypertension , and some types of cancer , often run in families, which suggests that heredity is at least partially responsible for their development. Congenital diseases , or birth defects, are disorders that are present at birth. Some are hereditary, others develop while a baby is in its mother's uterus or during the process of delivery. For example, if the mother contracts German measles , or rubella, during the early stages of pregnancy, her child may be born with heart defects, eye cataracts, deafness, or mental retardation . Use of alcohol during pregnancy can cause fetal alcohol syndrome, characterized by mental and physical retardation. Abnormal development of any body part in a fetus may produce a conge