Metastatic calcification involves a systemic calcium excess imbalance, which can be caused by hypercalcemia, kidney failure, milk-alkali syndrome, lack or excess of other minerals, or other causes.

Calcinosis cutis may be divided into the following types:

- Dystrophic calcinosis cutis

- Metastatic calcinosis cutis

- Iatrogenic calcinosis cutis

- Traumatic calcinosis cutis

- Idiopathic calcinosis cutis

- Idiopathic scrotal calcinosis

- Subepidermal calcified nodule

- Tumoral calcinosis

- Osteoma cutis

The most common type of calcinosis is dystrophic calcification. This type of calcification can occur as a response to any soft tissue damage, including that involved in implantation of medical devices.

The cause is not well defined. Originally considered idiopathic condition. Now accepted that majority of cases develop from dystrophic calcification of cyst contents.

Calcinosis cutis (or cutaneous calcification) is a type of calcinosis wherein calcium deposits form in the skin. A variety of factors can result in this condition. The most common source is dystrophic calcification, which occurs in soft tissue as a response to injury. In addition, calcinosis is seen in Limited Cutaneous Systemic Sclerosis, also known as CREST syndrome (the "C" in CREST). In dogs, calcinosis cutis is found in young, large breed dogs and is thought to occur after a traumatic injury.

Idiopathic scrotal calcinosis (also known as idiopathic calcified nodules of the scrotum) is a cutaneous condition characterized by calcification of the skin resulting from the deposition of calcium and phosphorus occurring on the scrotum. However, the levels of calcium and phosphate in the blood are normal. Idiopathic scrotal calcinosis typically affects young males, with an onset between adolescence and early adulthood. The scrotal calcinosis appears, without any symptoms, as yellowish nodules that range in size from 1 mm to several centimeters.

Tumoral calcinosis is a rare condition in which there is calcium deposition in the soft tissue in periarticular location i.e. around joints. The accumulations are outside the joint capsule. They are frequently seen in patients undergoing renal dialysis. It is also considered by some to have a hereditary predisposition. The name indicates calcinosis (calcium deposition) which resembles tumor (like a new growth). They are not true neoplasms - they don't have dividing cells. They are just deposition of inorganic calcium with serum exudate.

Children and adolescents (6 to 25 years) are the most commonly affected. The symptom that the accumulations cause is not pain but swelling around joints. They have propensity to enlarge progressively and ulcerate the overlying skin and extrude. They are most common around shoulders, hips and elbows. Laboratory evaluation reveal normal serum calcium levels and hyperphosphatemia. Rarely ALP (alkaline phosphatase - an enzyme active at sites of bone formation) may be elevated. Treatment is normalization of serum phosphate levels and resection of lesion. Surgical removal should be complete and if part of it is left, there is inevitable recurrence. Cutting through the excised calcium deposition reveals semifluid calcium suspension in albumin encapsulated by fibrous tissue.

Normophosphatemic familial tumoral calcinosis is a cutaneous disorder characterized by cutaneous calcification or ossification.

CREST causes thickening and tightening of the skin with deposition of calcific nodules ("calcinosis").

Raynaud's phenomenon is frequently the first manifestation of CREST/lcSSc, preceding other symptoms by years. Stress and cold temperature induce an exaggerated vasoconstriction of the small arteries, arterioles, and thermoregulatory vessels of the skin of the digits. Clinically this manifests as a white-blue-red transitions in skin color. Underlying this transition is pallor and cyanosis of the digits, followed by a reactive hyperemia as they rewarm. When extreme and frequent, this phenomenon can lead to digital ulcerations, gangrene, or amputation.

Ulceration can predispose to chronic infections of the involved site.

Myositis ossificans comprises two syndromes characterized by heterotopic ossification (calcification) of muscle.

Most (i.e. 80%) ossifications arise in the thigh or arm, and are caused by a premature return to activity after an injury. Other sites include intercostal spaces, erector spinae, pectoralis muscles, glutei, and the chest. On planar x-ray, hazy densities are sometimes noted approximately one month after injury, while the denser opacities eventually seen may not be apparent until two months have passed.

Milia-like calcinosis is a cutaneous condition characterized by small, milia-like lesions that develop on the dorsal surface of the hands and the face.

Sclerodactyly is a localized thickening and tightness of the skin of the fingers or toes. Sclerodactyly often leads to ulceration of the skin of the distal digits and is commonly accompanied by atrophy of the underlying soft tissues.

The term "sclerodactyly" is made up from the Greek "skleros" meaning hard and "daktylos" meaning a finger or toe – "hard fingers or toes".

It is sometimes associated with scleroderma and mixed connective tissue disease, auto-immune disorders.

Sclerodactyly is a component of the CREST variant of scleroderma (CREST is an acronym that stands for calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasia.)

Clinical diagnostic features are lifelong eruptions of pityriasis versicolor-like macules, flat wart-like papules, one to many cutaneous horn-like lesions, and development of cutaneous carcinomas.

Patients present with flat, slightly scaly, red-brown macules on the face, neck, and body, recurring especially around the penial area, or verruca-like papillomatous lesions, seborrheic keratosis-like lesions, and pinkish-red plane papules on the hands, upper and lower extremities, and face. The initial form of EV presents with only flat, wart-like lesions over the body, whereas the malignant form shows a higher rate of polymorphic skin lesions and development of multiple cutaneous tumors.

Generally, cutaneous lesions are spread over the body, but some cases have only a few lesions which are limited to one extremity.

Hypercementosis is an idiopathic, non-neoplastic condition characterized by the excessive buildup of normal cementum (calcified tissue) on the roots of one or more teeth. A thicker layer of cementum can give the tooth an enlarged appearance, which mainly occurs at the apex or apices of the tooth.

Though this condition is usually asymptomatic, if symptoms are present they are usually related to the causative process, (e.g. hypercalcemia). Some of the sympotoms that can happen are blood in the urine, fever and chills, nausea and vomiting, severe pain in the belly area, flanks of the back, groin, or testicles.

These include renal colic, polyuria and polydipsia:

- Renal colic is usually caused by pre-existing nephrolithiasis, as may occur in patients with chronic hypercalciuria. Less commonly, it can result from calcified bodies moving into the calyceal system.

- Nocturia, polyuria, and polydipsia from reduced urinary concentrating capacity (i.e. nephrogenic diabetes insipidus) as can be seen in hypercalcemia, medullary nephrocalcinosis of any cause, or in children with Bartter syndrome in whom essential tubular salt reabsorption is compromised.

There are several causes of nephrocalcinosis that are typically acute and present only with renal failure. These include tumor lysis syndrome, acute phosphate nephropathy, and occasional cases of enteric hyperoxaluria.

Nephrocalcinosis, once known as Albright's calcinosis after Fuller Albright, or Anderson-Carr kidneys, is a term originally used to describe deposition of calcium salts in the renal parenchyma due to hyperparathyroidism. The term nephrocalcinosis is used to describe the deposition of both calcium oxalate and calcium phosphate. It may cause acute kidney injury. It is now more commonly used to describe diffuse, fine, renal parenchymal calcification on radiology. It is caused by multiple different conditions and is determined progressive kidney dysfunction. These outlines eventually come together to form a dense mass. During its early stages, nephrocalcinosis is visible on x-ray, and appears as a fine granular mottling over the renal outlines. It is most commonly seen as an incidental finding with medullary sponge kidney on an abdominal x-ray.

However, it may be severe enough to cause (as well as be caused by) renal tubular acidosis or even end stage renal failure, due to disruption of the renal tissue by the deposited calcium.

Diffuse scleroderma can cause musculoskeletal, pulmonary, gastrointestinal, renal and other complications. Patients with greater cutaneous involvement are more likely to have involvement of the internal tissues and organs. Most patients (over 80%) have vascular symptoms and Raynaud's phenomenon, which leads to attacks of discoloration of the hands and feet in response to cold. Raynaud's normally affects the fingers and toes. Systemic scleroderma and Raynaud's can cause painful ulcers on the fingers or toes which are known as digital ulcers. Calcinosis (deposition of calcium in lumps under the skin) is also common in systemic scleroderma, and is often seen near the elbows, knees or other joints.

- Musculoskeletal

The first joint symptoms that patients with scleroderma have are typically non specific joint pains, which can lead to arthritis, or cause discomfort in tendons or muscles. Joint mobility, especially of the small joints of the hand, may be restricted by calcinosis or skin thickening. Patients may develop muscle weakness, or myopathy, either from the disease or its treatments.

- Lungs

Some impairment in lung function is almost universally seen in patients with diffuse scleroderma on pulmonary function testing; however, it does not necessarily cause symptoms, such as shortness of breath. Some patients can develop pulmonary hypertension, or elevation in the pressures of the pulmonary arteries. This can be progressive, and can lead to right-sided heart failure. The earliest manifestation of this may be a decreased diffusion capacity on pulmonary function testing.

Other pulmonary complications in more advanced disease include aspiration pneumonia, pulmonary hemorrhage and pneumothorax.

- Digestive tract

Diffuse scleroderma can affect any part of the gastrointestinal tract. The most common manifestation in the esophagus is reflux esophagitis, which may be complicated by peptic stricturing, or benign narrowing of the esophagus. This is best initially treated with proton pump inhibitors for acid suppression, but may require bougie dilatation in the case of stricture.

Scleroderma can decrease motility anywhere in the gastrointestinal tract. The most common source of decreased motility is the esophagus and the lower esophageal sphincter, leading to dysphagia and chest pain. As scleroderma progresses, esophageal involvement from abnormalities in decreased motility may worsen due to progressive fibrosis (scarring). If this is left untreated, acid from the stomach can back up into the esophagus, causing esophagitis and GERD. Further scarring from acid damage to the lower esophagus many times leads to the development of fibrotic narrowing, also known as strictures which can be treated by dilatation, and Barrett's esophagus.

Duodenum: In patients with neuromuscular disorders, particularly progressive systemic sclerosis and visceral myopathy, the duodenum is frequently involved. There may be dilatation, which is often more pronounced in the second, third and fourth parts. The dilated duodenum may be slow to empty and the grossly dilated, atonic organ may produce a sump effect.

The small intestine can also become involved, leading to bacterial overgrowth and malabsorption of bile salts, fats, carbohydrates, proteins, and vitamins. The colon can be involved, and can cause pseudo-obstruction or ischemic colitis.

Rarer complications include pneumatosis cystoides intestinalis, or gas pockets in the bowel wall, wide mouthed diverticula in the colon and esophagus, and liver fibrosis. Patients with severe gastrointestinal involvement can become profoundly malnourished.

Scleroderma may also be associated with gastric antral vascular ectasia (GAVE), also known as "watermelon stomach". This is a condition where atypical blood vessels proliferate usually in a radially symmetric pattern around the pylorus of the stomach. GAVE can be a cause of upper gastrointestinal bleeding or iron deficiency anemia in patients with scleroderma.

- Kidneys

Renal involvement, in scleroderma, is considered a poor prognostic factor and frequently a cause of death.

The most important clinical complication of scleroderma involving the kidney is "scleroderma renal crisis". Symptoms of scleroderma renal crisis are malignant hypertension (high blood pressure with evidence of acute organ damage), hyperreninemia (high renin levels), azotemia (kidney failure with accumulation of waste products in the blood) and microangiopathic hemolytic anemia (destruction of red blood cells). Apart from the high blood pressure, hematuria (blood in the urine) and proteinuria (protein loss in the urine) may be indicative.

In the past scleroderma renal crisis was almost uniformily fatal. While outcomes have improved significantly with the use of ACE inhibitors the prognosis is often guarded, as a significant number of patients are refractory to treatment and develop renal failure. Approximately 5–10% of all diffuse cutaneous scleroderma patients develop renal crisis at some point in the course of their disease. Patients that have rapid skin involvement have the highest risk of renal complications. It is most common in diffuse cutaneous scleroderma, and is often associated with antibodies against RNA polymerase (in 59% of cases). Many proceed to dialysis, although this can be stopped within three years in about a third of cases. Higher age and (paradoxically) a lower blood pressure at presentation make it more likely that dialysis is needed.

Treatments for scleroderma renal crisis include ACE inhibitors. Prophylactic use of ACE inhibitors is currently not recommended, as recent data suggest a poorer prognosis in patient treated with these drugs prior to the development of renal crisis. Transplanted kidneys are known to be affected by scleroderma and patients with early onset renal disease (within one year of the scleroderma diagnosis) are thought to have the highest risk for recurrence.

Primary pigmented nodular adrenocortical disease (PPNAD) was first coined in 1984 by Carney et al. it often occurs in association with Carney complex (CNC). CNC is a rare syndrome that involves the formation of abnormal tumours that cause endocrine hyperactivity.

PPNAD arises due to the enlargement of the cortex of the adrenal glands, resulting in Cushing's syndrome that is independent of the pituitary hormone ACTH.

It is experienced as an uncomfortable sensation in the tooth, followed by an aching pain.

It may be noted on radiographs as a radiopaque (or lighter) mass at each root apex.

Epidermodysplasia verruciformis (EV), also known as treeman syndrome, is an extremely rare autosomal recessive hereditary skin disorder associated with a high risk of skin cancer. It is characterized by abnormal susceptibility to human papillomaviruses (HPVs) of the skin. The resulting uncontrolled HPV infections result in the growth of scaly macules and papules, particularly on the hands and feet. It is typically associated with HPV types 5 and 8, which are found in about 80% of the normal population as asymptomatic infections, although other types may also contribute.

The condition usually has an onset of between the ages of one and 20 but can occasionally present in middle age. The condition is also known as Lewandowsky–Lutz dysplasia – named after the physicians who first documented it, Felix Lewandowsky and Wilhelm Lutz.

PPNAD is a rare cause of high cortisol levels in the blood and often manifests as ACTH-independent Cushing's syndrome. The effects of PPNAD can often be cyclical so the symptoms of Cushing's syndrome will not always be as severe, which may complicate diagnosis. The classic symptoms of Cushing's syndrome include rapid central weight gain, a puffy red face and a buffalo hump at the back of the neck due to fat deposits. Skin changes in Cushing's syndrome include thinning and bruising easily, developing striae and hyperpigmentation at skin folds. The hormonal changes can lead to hirsuitism, males developing breast tissue, females no longer having periods and both sexes may become infertile. High cortisol levels can lead to psychological disturbances such as anxiety or depression and insomnia. Bone health can deteriorate, leading to an increased fracture risk in people with Cushing's syndrome. PPNAD is unique as it often causes Cushing's at a young age, in children and adolescents. In addition to the other symptoms of Cushing's syndrome, the patient may have a short stature due to interrupted growth because of ACTH suppression.

In 90% of people with PPNAD it is associated with Carney Complex. Carney Complex is usually inherited, however it can also occur sporadically. A visible sign of Carney complex is abnormal skin hyperpigmentation. There may also be myxomas which can appear as lumps in the skin and breast as well as often being present in the heart, which can lead to multiple cardiovascular problems. The majority of people with PPNAD will have some of these signs/symptoms due to the strong association between PPNAD and Carney Complex.

In the skin, systemic sclerosis causes hardening and scarring. The skin may appear tight, reddish, or scaly. Blood vessels may also be more visible. Where large areas are affected, fat and muscle wastage may weaken limbs and affect appearance. Patients report severe and recurrent itching of large skin areas. The severity of these symptoms varies greatly among patients: Some having scleroderma of only a limited area of the skin (such as the fingers) and little involvement of the underlying tissue, while others have progressive skin involvement. Digital ulcers — open wounds on especially on fingertips and less commonly the knuckles — are not uncommon.

Goldman states that "numerous inherited or congenital conditions display cutaneous telangiectasia".

These include:

- Naevus flammeus (port-wine stain)

- Klippel-Trenaunay syndrome

- Maffucci's syndrome (multiple enchondromas & hemangiomas)

- Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome)

- Ataxia-telangiectasia

- Sturge-Weber syndrome, a nevus formation in the skin supplied by the trigeminal nerve and associated with facial port-wine stains, glaucoma, meningeal angiomas and mental retardation

- Hypotrichosis–lymphedema–telangiectasia syndrome, caused by mutation in transcription factor "SOX18"