Q: Is it true that certain diseases such as blood pressure, diabetes, cancer or arthritis are hereditary? If one of the parents has it then children will also have it. Please clarify.

A:The role of heredity in various diseases is being extensively evaluated but exact data is not available.

The incidence of hypertension is 30-60% higher if there is a strong family history. Diabetes is of two types - type 1 and type 2. Both have a genetic basis but a lot of environmental factors also come into play. Genes alone are not enough. One proof of this is in identical twins. If one twin has diabetes, the other gets the disease at most only half the time. When one twin has type 2 diabetes, the other's risk is at most 3 in 4. So the risk of a genetic basis is stronger in adult type of diabetes or type 2 diabetes. In general, if a person has type 2 diabetes, the risk of his child getting diabetes is 1 in 7 if the person was diagnosed before age 50 and 1 in 13 if he was diagnosed after age 50. Different arthritis has different heredity patterns. The incidence of rheumatoid arthritis in first-degree relatives is only 0.8% compared to 0.5% in general population. SLE has a higher association with a study showing 8% of patients with SLE having a first-degree family member with SLE. Osteoarthritis is not an autoimmune disorder but the risk maybe 2-7 fold higher if there is a strong family history.

Cancers in the family may be due to abnormal genes such as kidney cancer, colon, breast or ovarian cancer, sarcoma etc. The history of cancer at a young age or certain associations like hereditary breast and ovarian cancer syndrome (HBOC) and hereditary non-polyposis colorectal cancer (HNPCC) are important and other family members should be screened.

A number of these diseases are multifactorial and not purely based on genetics. Modifiable risks include lifestyle factors - diet, exercise, smoking, tobacco and alcohol. It is important to be vigilant but not to be overwhelmed by the data on heredity.