The word miasm (deriving from the Greek miainein 'to pollute') is a homeopathic term for the infectuous principle, which when taken in by the organism may cause disease. A miasm may be inherited, acquired or acute.
The main miasms are psora (derived from scabies), sycosis (from gonorrhea) and syphilis (from syphilis). Other illnesses such as tuberculosis, cancer, drug abuse are also considered to be miasmatic (passed on to offspring).
If one of your ancestors has had scabies, gonorrhea or syphilis the miasm is passed on to you as a predisposition or active illness, possibly with a physical deformity.
A classical homeopath is trained to take this into account and take the appropriate steps to treat the miasm or miasms concerned.
As a patient it is important to be aware of this miasmatic inheritance and not pass it on to one's children but have it treated first.
If one has had scabies, gonorrhea or syphilis prior to having children, it would be wise to treat them homeopathically for it.
A family history of tuberculosis, cancer or drugs prior to having children would also warrant treating them for such.