Hydroxyapatite Deposition Disease (HADD) is a condition characterized by the abnormal accumulation of hydroxyapatite crystals in soft tissues, particularly around joints and tendons, leading to inflammation and pain. Clinically, it is significant as it can mimic other musculoskeletal disorders, potentially delaying appropriate treatment. A common association is calcific tendinitis, often affecting the shoulder, which can result in significant functional impairment if not addressed.