Makindo Medical Notes

Commonest causes are hyperparathyroidism, sarcoidosis, metastatic disease, and myeloma and may be seen in patients with hypermetabolic states who have undergone prolonged periods of bed rest

About

• Metastatic calcification is the deposition of calcium salts in previously normal tissue;

Aetiology

• Increase in the calcium × phosphate product, and as a consequence amorphous calcium phosphate is precipitated in organs, blood vessels and soft tissues

Causes

• Raised Parathormone, Hypercalcaemia
• Amyloidosis
• Renal failure with raised phosphate
• Addison's disease (adrenal calcification)
• TB nodes
• Toxoplasmosis (CNS), Histoplasmosis (e.g. in lung)
• Overdose of vitamin D;
• Raynaud's-associated diseases (SLE, SS, dermatomyositis)
• Muscle primaries/leiomyosarcomas)
• Ossifying metastases (Osteosarcoma) or Ovarian mets (to peritoneum)
• Nephrocalcinosis
• Endocrine tumour (e.g. gastrinoma).

Common Causes

• Hyperparathyroidism: Excessive secretion of parathyroid hormone (PTH) causes increased calcium mobilization from bones and increased calcium reabsorption by the kidneys.
• Renal failure: Reduced renal excretion of phosphate leads to secondary hyperparathyroidism and calcium-phosphate imbalance.
• Malignancies: Cancers such as multiple myeloma, breast cancer, and squamous cell carcinoma can cause hypercalcemia due to osteolytic activity or paraneoplastic syndromes.
• Vitamin D intoxication: Excessive vitamin D increases intestinal absorption of calcium, leading to hypercalcemia.
• Granulomatous diseases: Conditions like sarcoidosis and tuberculosis increase calcitriol production, leading to hypercalcemia.

Pathology

• The calcification may be both intracellular and extracellular. Mineral deposition is particularly likely to occur in the kidneys, alveolar walls of the lungs, cornea, conjunctiva, and gastric mucosa as well as in the media and intima of the peripheral arteries.

Pathophysiology

• Metastatic calcification occurs when elevated serum calcium-phosphate product exceeds the solubility threshold, leading to precipitation of calcium salts in normal tissues. Unlike dystrophic calcification, this occurs in the absence of tissue injury or necrosis.
• Increased serum calcium: Hypercalcemia from any cause raises the calcium-phosphate ratio, leading to mineral deposition in tissues.
• Tissue predilection: Calcification typically occurs in tissues that have an alkaline environment or that handle large volumes of bodily fluids, such as the lungs, kidneys, stomach, and blood vessels.

Commonly Affected Sites

• Metastatic calcification most commonly affects tissues with a high metabolic rate or those with alkaline environments.
• Lungs: Calcification occur in the alveolar walls and bronchial tissues, often impairing respiratory function.
• Kidneys: Deposits form in the renal parenchyma and tubules, leading to nephrocalcinosis and impaired renal function.
• Stomach: Calcium deposition in the gastric mucosa can cause gastritis and impair acid secretion.
• Heart and Blood Vessels: Calcifications can occur in the myocardium, cardiac valves, and arteries, leading to cardiovascular complications.

Clinical Presentation

• Symptoms of metastatic calcification depend on the organs affected and the severity of calcification.
• Respiratory symptoms: Dyspnea, chronic cough, and reduced lung capacity due to pulmonary calcifications.
• Renal symptoms: Polyuria, polydipsia, and progressive renal insufficiency due to nephrocalcinosis.
• Gastrointestinal symptoms: Nausea, vomiting, and epigastric pain due to calcification of the stomach lining.
• Cardiovascular symptoms: Hypertension, arrhythmias, and heart failure in cases with cardiac or vascular involvement.

Diagnosis

• The diagnosis of metastatic calcification involves identifying hypercalcemia and assessing the extent of tissue involvement.
• Serum studies: Elevated serum calcium, phosphate, and parathyroid hormone (PTH) levels. Assessing vitamin D levels and renal function tests are also essential.
• Imaging: X-rays, CT scans, and MRIs can reveal calcified deposits in various tissues.
• Biopsy: Tissue biopsy may be performed to confirm calcium deposition in affected tissues.

Treatment

• The treatment of metastatic calcification focuses on managing the underlying cause of hypercalcaemia and addressing complications.
• Hypercalcaemia management: Includes hydration, diuretics (e.g., furosemide), bisphosphonates, and calcitonin to reduce serum calcium levels.
• Parathyroidectomy: Indicated in cases of primary hyperparathyroidism or refractory secondary hyperparathyroidism.
• Dialysis: Used in patients with renal failure and hypercalcaemia who do not respond to medical management.
• Monitor affected organs: Regular monitoring of lung function, renal function, and cardiovascular health is essential.

Prognosis

The prognosis of metastatic calcification depends on the underlying cause and the extent of organ involvement. Early detection and management of hypercalcaemia can prevent further tissue damage.