Iatrogenic calcification refers to deposition of calcium salts as a result of medical intervention, usually intravenous calcium chloride or calcium gluconate [3–5]. The etiology is thought to be both locally elevated tissue concentration of calcium, and tissue injury at the site of extravasated calcium.

Soft tissue calcification commonly complicates chronic renal failure: estimates regarding its prevalence range from approximately 40 %, to as high as 80 % in one autopsy study of hemodialysis patients [6]. Please see Chap. 10 for details on clinical presentation and treatment of calciphylaxis.

The most common type of cutaneous calcification seen in CKD is metastatic calcification.Benign nodular calcification, the most common subtype, is defined as cutaneous and subcutaneous tissue calcification in the absence of tissue necrosis. Lesions are typically painless, firm, papules, plaques or nodules that occur most commonly around joints and on the fingertips [7, 8]. Long-standing secondary hyperparathyroidism predisposes to this condition; the number and size of the calcium deposits are directly proportional to the degree of hyperphosphatemia. Similar findings are seen in tumoral calcinosis, an inherited or acquired abnormality of phosphate homeostasis independent of renal function [9].Although it is often seen in otherwise healthy individuals, it might also be triggered by the uremic mileu.

Dystrophic calcification in CKD is more commonly observed in patients with connective tissue diseases, especially CREST syndrome (calcinosis cutis, Raynaud phenomenon, esophageal dysfunction, sclerodactyly, and telangiectasia) and lupus panniculitis.However, it can also be seen in patients with comorbidities including pancreatic panniculitis, various inherited disorders such as Ehlers-Danlos, cutaneous neoplasms (pilomatricomas, pilar cysts), and infections (onchocerciasis, cysticercosis).Calcified lesions are usually localized to the area affected by the underlying condition.

Iatrogenic calcification occurs as a complication of a procedure, such as extravasation during intravenous administration of solutions containing calcium or phosphate or prolonged contact with calcium chloride electrode paste during electroencephalography [9]. Lesions develop at the site of the inciting event.

Though uncommon, idiopathic calcinosis can also be seen in patients with CKD.Subepidermal calcified nodules present as isolated hard 3–11 mm white-to-yellow papules over the head and extremities, usually in children. These might represent calcified adnexal structures according to one study [10]. Scrotal calcinosis, characterized by marble-like subcutaneous nodules varying in size and number, are thought to arise from epidermal or eccrine cysts. They are usually asymptomatic although minimal pruritus or a white chalky discharge may be noted.Milia-like calcinosis consists of tiny white pearly papules (“milia-like” lesions) on the dorsal surface of the hands and face; they are most commonly seen in patients with Down syndrome. Although there are usually no preexisting lesions, some appear to due to calcification of pre-existing syringomas.

Milia-like calcinosis characterized by tiny white pearly papules (“milia-like” lesions) on the dorsal surface of the hands and face, most commonly seen in the setting of Down syndrome. There are usually no preexisting lesions, although in some patients they appear to arise from calcification of precursor syringomas.

In metastatic calcification, theoretically, precipitation occurs when levels of calcium and phosphate exceed their solubility product, although one study found clinically elevated calcium or phosphate levels in only a fraction of patients with metastatic calcification [11].

Serum calcium and phosphate levels are within normal limits in dystrophic calcification and in idiopathic calcification (except for tumoral calcinosis).