This is a question that everyone acquainted with the idea of reincarnation must ask. My research of the Cayce readings has led me to the conclusion that most serious, long-term, degenerative diseases - like Parkinson's disease, rheumatoid arthritis, amyotrophic lateral sclerosis and muscular dystrophy are karmic in nature. Seemingly conflicting viewpoints about the reversibility potential of these diseases can be found in world literature, in the Bible and in the readings.
However, there is always a point where karma ceases. Since it really is a debt, it can be paid off like any other debt. No written law states that the debt must be paid; however, the disease process ends with death of the physical body. So there is a point where karma ends - a place of spiritual understanding where the lessons are well taught and well learned. We might call this process "Where Karma Ends and Grace Begins." (Hugh Lynn Cayce has spoken on that subject many times over the years.) What we call grace seems to be a point of forgiveness, accepted by the person experiencing the karma. The forgiveness may have been offered for a long time, but acceptance of it may have been delayed. The Cayce material appears to lend credence to the concept that rejection is rebellion and rebellion is sin - as is the disease, expressed as "sin lying at your own doorstep." Acceptance, then, must be - in this format of thinking - a portion of the healing process, and must be a part of the spiritual learning that an entity undergoes during the time he spends on this earth.
In the case of a person with Parkinson's disease, who had asked about building immunity, the Cayce source offered the following information:
If precautionary measures are kept, as to producing the correct vibrations; that is, loosing certain electrical forces - as with the healing waves from the open machine - these should keep away any infectious tendencies. For, even karmic forces will be met in definite spiritual purposes. (3011-2)
If karmic forces can be met in definite spiritual purposes, then the physician working with a patient with an "incurable" disease is challenged to treat such a person as an individual who may, at any moment, find that he has learned the lesson inherent in the experience. His treatment program must then have a spiritual direction, engaging the mind in the total educational process. And the physician must work patiently with those trying to overcome that which has become part of their total life experience.
It's interesting when one approaches the healing of the body from the standpoint of an adventure into that person's consciousness and an opportunity to experience grace becoming active through the disease process.
[Note: The preceding report was written by William McGarey, M. D. and is excerpted from The A.R.E. Journal, September, 1977, Volume 12, No. 5, page 228, Copyright © 1977 by the Edgar Cayce Foundation, Virginia Beach, VA.]