“…The serum creatinine was 63 (normal < 106 ~tmol/l), calcium 2.38 (norIt is well known that monosodium urate (gout) and calcium pyrophosphate (pseudogom) may induce a crystal synovitis but the role of hydroxyapatite (HA) is often overlooked. Although, hydroxyapatite deposition disease (HADD) may be asymptomatic, it usually causes bursitis, periarthritis, or frank arthritis and may even involve subcutaneous tissues [1,2,3].…”