ABSTRACT
Basic calcium phosphate (BCP) crystals include hydroxyapatite, octacalcium
phosphate, tricalcium phosphate and magnesium whitlockite, although the most
abundant of these crystal species in apatite-associated syndromes is hydro-
xyapatite. Hydroxyapatite is represented by the formula Ca10(PO4)6(OH)2 and
generally occurs in the partially carbonate-substituted form. Octacalcium
phosphate (Ca8H2(PO4)6$5H2O) and tricalcium phosphate (Ca3(PO4)2) also occur. Although these crystals may form deposits that are asymptomatic, they
are associated with a number of clinical syndromes (see Chapter 7). In vitro
experiments have demonstrated a number of effects of BCP crystals that may
contribute to the pathogenesis of these BCP crystal-associated syndromes (1).
This chapter reviews the biochemical basis that underlies these clinical and
laboratory observations.
