Autophagy in relationship to disease. Autophagy is a lysosomal degradation pathway that is essential for survival, differentiation, development, and homeostasis. Autophagy serves an adaptive role to protect organisms against diverse pathologies. However, in certain experimental disease settings, the self-cannibalistic or, paradoxically, even the prosurvival functions of autophagy may be deleterious. This review summarizes advances in understanding the functions of autophagy and its possible roles in the causation and prevention of human diseases.