HETEROTOPIC (EXTRAOSSEOUS) CALCIFICATION (CALCINOSIS) - ETIOLOGY, PATHOGENESIS AND CLINICAL IMPORTANCE

Heterotopic tissue calcification represents a pathological event which goes along with active extra-and intracellular metabolic processes. T he heterotopic calcification is not the manifestation of tissue ageing . Aetiologically, metastatic calcification, dystrophic calcification a nd genetic-hereditary calcification are distinguished. Two pathogeneti c mechanisms play a role during the heterotopic calcification. The int racellular calcific is based upon the function of mitochondria as regu lator of the calcium concentration and as ''lime-catcher''. The extrac ellular calcification is initiated by membraneous organelles - so-call ed matrix vesicles. The further steps are the production of hydroxylap atite crystals which are eliminated from the matrix vesicles in the ex tracellular spaces. Special types of heterotopic calcification are hyp ercalcaemias (tumour-associated hypercalcaemias, primary and tertiary hyperparathyroidism, drug-induced hypercalcaemias),tumoral calcinosis, intratumoral calcifications, calcifications of different organs (lung , heart, vessels,joints, ligaments, skin or kidney). Some calcificatio ns of organs show partly overlapping aetiological factors and pathogen etic mechanisms.