Calcium deposition is a disease that results from the deposition of insoluble calcium salts in the tissues. They are classified as idiopathic, metastatic and dystrophic. Idiopathic calcium deposits are mostly of unknown origin, while metastatic calcium deposits are secondary to disorders of calcium and phosphorus metabolism, such as hyperparathyroidism, multiple myeloma, and phosphate retention due to renal insufficiency. Dystrophic calcium deposition mostly occurs secondary to skin or tissue injury. Causes of alkaline calcium phosphate crystal deposition disease: Alkaline calcium phosphate crystal deposition within the pars tendineae was once thought to be secondary to ectopic calcification due to tendon injury, so the classic descriptions of the disease often associate it with overuse or trauma to the shoulder joint. However, cases of bilateral or multifocal paracartilaginous calcification are not uncommon. It is well established that the disease can be secondary to a number of underlying disorders of abnormal calcium and phosphorus metabolism, such as chronic renal failure, diabetes mellitus, rheumatic disease, thyroid or parathyroid disease, and tumors. Other types of crystals, such as calcium oxalate crystals and calcium pyrophosphate crystals, are often found, which further suggests a close association between secondary alkaline calcium phosphate deposition disease and abnormal calcium and phosphorus metabolism. However, the predilection for the disease does not seem to be clearly related to these underlying diseases, and studies related to the genetic factors or HLA typing of the disease have not been conclusive.