Generalised atrophy can occur from starvation and also through the later stages of malignant disease. (e.g. carchexia.) The reduction in the size of the tissues and/organs is not specific.
Tissue-specific atrophy unlike generalised atrophy, only affects a specific tissue or organ system in the body. This normally occurs when there's a change directly involving that part of the body. (e.g. a leg that is in a cast for 6 weeks due to a fracture would undergo serious skeletal muscle atrophy).