Family history (medicine)

In medicine, a family history consists of information about disorders from which the direct blood relatives of the patient have suffered. Genealogy typically includes very little of the medical history of the family, but the medical history could be considered a specific subset of the total history of a family. Accurate knowledge of a patient's family history may identify a predisposition to developing certain illnesses, which can inform clinical decisions and allow effective management or even prevention of conditions.

Uses
Although sometimes neglected, many healthcare professionals glean information on family morbidity of particular diseases (e.g. cardiovascular diseases, autoimmune disorders, mental disorders, diabetes, cancer) to assess whether a person is at risk of developing similar problems.

Family histories may be imprecise because of various possible reasons:
 * Adoption, fostering, illegitimacy and adultery
 * Lack of contact between close relatives
 * Uncertainty about the relative's exact diagnosis
 * In complex situations, a family tree or genogram may be used to organize the resulting information.

Some medical conditions are carried only by the female line such as X-linked conditions and some  Mitochondrial diseases. Tracing female ancestors can be difficult in societies that change the woman's family name when she marries. Death records often give the maiden name of the deceased, and possibly also the deceased's mother’s maiden name. Some of the most useful records for tracing women are wills and probate records.

Other medical conditions are carried only by the male line, though these Y-linked conditions are rare owing to the small size of the Y Chromosome. Tracing male ancestors may be impossible if the conception is due to rape or sexual activity outside of a marriage.

Consequences
Not all positive family histories imply a genetic cause. If various members of the same family have been exposed to the same toxin, then they may develop similar symptoms without a genetic cause.

If a patient has a strong family history of a particular disorder (or group of disorders), this will generally lead to a lower threshold for investigating symptoms or initiating treatment. This is seen particularly in cardiac disease, where a strong family history is considered a significant cardiovascular risk factor.

In diseases with a known hereditary component, many otherwise healthy people with a positive family history are tested early, with the aim of an early diagnosis and intervention to prevent the symptoms from developing. This has become accepted in hemochromatosis and various other disorders.