Dyscrasia is where there is a blocking layer from either disease or toxicity, aquired miasmatically, or in utero or subsequently, that affects the patient's ability to recover.

Examples:

Mercury toxicity
Vaccinations
Radioactivity

Dyscrasia
(n.) An ill habit or state of the constitution; -- formerly regarded as dependent on a morbid condition of the blood and humors. An abnormal or physiologically unbalanced state of the body. The term "dyscrasia" was borrowed from the Greek meaning "a bad mixture" referring to imbalance between the four humors which caused disease.