From the earliest times Jewish scholars have had a keen eye for diseases that were suspected to be hereditary in nature.
The Talmud (Yevamot 64B) forbids the circumcision of a baby if his two brothers bleed to death following the procedure. If two sisters each lose a son after circumcision, a baby boy born to the third should not be circumcised.
The best known of all Jewish diseases is Tay Sachs, a lethal disorder of excess fat storage in the central nervous system. It causes progressive mental deterioration and death by five years of age. A recessive gene carries Tay Sachs disease. This means that a person can have one gene for Tay Sachs and still not suffer the disease. Such a person is called a carrier. If two carriers marry, the odds are that each will provide a Tay Sachs gene in half their sperm and eggs. Therefore, on average, one-quarter of their offspring will get Tay Sachs disease.
Tay Sachs is now a predictable disease due to modern technology. A simple blood test is now available to determine if a person is a Tay Sachs carrier. One in 30 Ashkenazi Jews are carriers, and one in 3600 is actually afflicted with the disease. If both parents are carriers, the fetus can be tested in utero at the end of 14 weeks of pregnancy.
Another Jewish genetic disease is Niemann-Pick disease. This also results in the abnormal accumulation of fats within the body. It is a condition that is similar to Tay Sachs and has a similar lethal course, resulting in early death. This is a very rare disease, affecting only one in 40,000 people. Gaucher’s disease is another fat storage disease; the most prevalent of the three, with one case per every 2500 Jews. The families of almost everyone affected by these diseases can be traced back to the northeastern provinces of Poland and the Baltic States.
Jews are also found to suffer from hemorrhoids at a higher rate than non-Jews. This is not a recent problem. In the 15th century, Rabbi Isaac Abarbanel wrote: “It is always found that Jews suffer from acute fever, pestilence, and hemorrhoids more than any other nation.” Several reasons have been given for this phenomenon. In the 14th century Bernard de Gordon suggested the following reasons: “They are generally sedentary they are usually in fear and anxiety and therefore the melancholy blood becomes increased”.
Depression and various neuroses have been attributed to Jews in excess, and studies have supported this contention. Schizophrenia, on the other hand, is said to be rarer among Jews than among the general population.
The study of Jewish genetic disease is, like other areas of medicine, an endless process of research and discovery. It reveals far more about Jews than typically suffered symptoms.