METASTATIC CALCIFICATION

PATHOLOGIC CALCIFICATION

• Definition – Abnormal deposition of calcium salts in the tissue other than osteoid or enamel. Along with calcium salts, small amounts of Magnesium, iron and other mineral salts are also deposited

• Two types of pathologic calcifications are-

  • Dystrophic calcification

  • Metastatic calcificatioN

• Metastatic calcification

  • This type of calcification occurs in conditions where there is hypercalcemia

  • It is named as metastatic calcificaion as calcium from bone  is moved out and deposited in the distant tissues

  • Causes of metastatic calcification

    • Hyperparathyroidism – Increased secretion of parathyroid hormone leads to bone resorption. It occurs in conditions like

      • Parathyroid hyperplasia

      • Parathyroid tumors

      • Ectopic secretion of PTH- related protein by malignant tumors

    • Resorption of bone tissue – It occurs in 

      • Tumors of bone marrow (eg. Multiple myeloma, leukemia )

      • Diffuse skeletal metastasis (in breast cancer)

      • Accelerated bone turnover (pagets disease)

      • immobilization

    • Disorders of Vitamin D

      • Vitamin D intoxication (hypervitaminosis)

      • Sarcoidosis – in this condition macrophages activate Vit D precursors

      • Idiopathic hypercalcemia of infancy – sensitivity of Vitamin D is very high.

    • Renal failure- this leads to secondary hyperparathyroidism due to retention of phosphate

    • Miscellaneous causes –

      • Aluminium intoxication occurring in patients with chronic renal dialysis

      • Milk alkali syndrome due to excessive intake of milk

  • Sites of metastatic calcification– May occur through out the body but mainly affects the interstitial tissue of the organs which excrete acid and have internal alkaline compartment that predisposes to calcium deposition .  Most common organs are

    • Gastric mucosa

    • Kidneys

    • Lungs

    • Systemic arteries Pulmonary veins

  • Morphology –

    • Grossly calcium deposition occurs as fine, white granules or clumps which are gritty

    • Microscopically, on Haematoxylin and Eosin stained sections, calcium appears as basophilic, amorphous granular or clumped

    • Heterotopic bone may be formed in the foci of calcifications

    • Special stain for calcium salts – VonKossa stain ( Calcium appears black in colour)

• Clinical features – Pathologic calcification dose not produce clinical dysfunction but massive depositions in organs can damage the organ (eg. Nephrocalcinosis producing renal damage)

References

1. Dr.A.K.Mandal, Dr. Sharmana Choudhury. Textbook of Pathology. Second edition. 2017

2. Kumar, Abbas, Aster. Robbins and Cotran. Pathologic Basis of Disease. 9th edition.2018