Calcinosis is the abnormal deposition of calcium salts in body tissues outside the skeleton, forming hard nodules in skin, muscles, or organs. It occurs in several forms: dystrophic calcification follows tissue damage, metastatic calcification follows high blood calcium or phosphate, and idiopathic forms have no clear cause. It complicates conditions such as kidney failure, where mineral balance is disturbed, and autoimmune diseases like scleroderma. The deposits can be painful and restrict movement. Management addresses the underlying disorder and mineral imbalance, sometimes with dietary phosphate restriction. It illustrates how tightly the body normally controls calcium placement.