Calcinosis (hydroxyapatite and calcium phosphate crystal deposition) within the extracellular matrix of the dermis and subcutaneous tissue is a frequent manifestation of adult and pediatric systemic autoimmune rheumatic diseases, specifically systemic sclerosis, dermatomyositis, mixed connective tissue disease, and systemic lupus erythematosus. In this article, we review classification of calcinosis, highlight mechanisms that may contribute to the pathogenesis of calcinosis, and summarize the evidence evaluating nonpharmacologic and pharmacologic interventions for the treatment of calcinosis.