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Hydroxyapatite Deposition DiseaseStephen F. Quinn, M.D.
Findings
Analysis
Hydroxyapatite deposition illness (HADD), with calcium hydroxyapatite crystal deposition alongside the bursal floor of the supraspinatus tendon.
Introduction – “calcium hydroxyapatite deposition”
Hydroxyapatite deposition illness (HADD) refers to a spectrum of abnormalities that features calcific tendinitis, different periarticular hydroxyapatite deposition, and hydroxyapatite induced arthritis.1,2 Different names for HADD embody calcific tendinosis, peritendinitis calcarea, calcific peritendinitis and bursitis, and hydroxyapatite rheumatism.3 Calcium hydroxyapatite (CHA) is the most typical kind of calcium in human bone and can also be the most typical pathologic calcification discovered within the physique.4 CHA, in addition to different primary calcium phosphate crystals, are thought-about the causal brokers in some entities. In different conditions, the essential calcium phosphates are thought-about secondary to underlying illnesses. For instance, the calcifications related to extreme renal illness, collagen vascular illness (dermatomyositis and scleroderma), power neurologic circumstances, Vitamin D overload, tumoral calcinosis and dystrophic calcification are composed largely of CHA.4
Pathogenesis
CHA deposits happen in tendons, peritendinous tissues, bursae, and ligaments. The pathogenesis of periarticular CHA deposits is unsure and a number of other explanations have been supplied. Potential etiologies for CHA deposition embody native trauma, ischemia, and necrosis of tendons. CHA deposits within the supraspinatus tendon are sometimes positioned within the poorly vascularized essential zone, which is a couple of millimeters medial to the osseous insertion. CHA deposits in different tendons happen preferentially in hypovascular segments, supporting the speculation that native necrosis results in crystal deposition.3 CHA deposition is a cell-mediated course of the place tissue adjustments lead to transformation of tendinous tissues into chondrocytes. The CHA crystals are deposited in an extracellular matrix derived from the chondrocytes.5 Metabolic and genetic elements can predispose sufferers to CHA deposition.4
Laboratory Findings
Laboratory checks are normally damaging in sufferers with HADD. CHA crystals are 75-250 nm, and are usually not seen with gentle microscopy, besides when the crystals kind aggregates. The CHA crystals are non-birefringent in polarized gentle. Transmission electron microscopy or electron diffraction research are wanted to determine CHA crystals. Alizarin purple S stain reportedly is a delicate however non-specific software for screening for CHA crystals.6