Why do some diseases disappear while others persist for years, change form and return again and again? Why does eczema become asthma, allergy become arthritis, or chronic stress end in degeneration and cancer? Samuel Hahnemann believed that behind such conditions there exist deep and persistent tendencies called miasms. In this remarkable work, the classical doctrine of psora, sycosis, syphilis, tubercular and cancer miasms is reinterpreted through the language of modern science. Drawing upon immunology, endocrinology, genetics, epigenetics, biochemistry, systems biology and chronic inflammation, the authors show how the ancient concept of miasm may correspond to stable patterns of biological dysregulation. A major work for physicians, teachers, researchers and serious students of homoeopathy.