Multiple juxta-articular deposits of hydroxyapatite causing calcific periarthritis may be a useful sign of hypophosphatasia, especially when the calcific periarthritis is familial.
ypophosphatasia (HPP) is the inborn error of metabolism that features low serum alkaline phosphatase (ALP) activity caused by loss-of-function mutation(s) within the gene for the tissue nonspecific isoenzyme of ALP (TNSALP). In HPP, extracellular accumulation of inorganic pyrophosphate (PPi), a TNSALP substrate and inhibitor of mineralization, leads frequently to premature tooth loss and often to rickets or osteomalacia. In affected adults, the excess PPi sometimes also causes calcium pyrophosphate dihydrate (CPPD) deposition, PPi arthropathy, or pseudogout, or seemingly paradoxical deposition of hydroxyapatite crystals in ligaments or around joints when the condition is called calcific periarthritis (CP).
Autor: Guañabens N, Mumm S, Möller I, González-Roca E, Peris P, Demertzis JL, Whyte MP.