TY - JOUR T1 - Mixed Crystal Disease: A Tale of 2 Crystals JF - The Journal of Rheumatology JO - J Rheumatol SP - 1158 LP - 1159 DO - 10.3899/jrheum.191316 VL - 47 IS - 8 AU - ELISEO PASCUAL AU - FRANCISCA SIVERA AU - MARIANO ANDRES Y1 - 2020/08/01 UR - http://www.jrheum.org/content/47/8/1158.abstract N2 - A report published in this issue of The Journal estimated the recurrence rate of acute calcium pyrophosphate (CPP) crystal arthritis and its associated factors1 on 111 patients with a first acute flare of CPP arthritis. Of these, 13 were considered to have gout on top of fulfilling the study’s definition of acute CPP crystal arthritis: 1 had monosodium urate (MSU) crystals documented on a different occasion in a different joint, 1 had simultaneous observation of MSU and CPP crystals in the same joint, 7 had prior podagra, and 4 had been diagnosed with gout based on elevated uric acid and synovitis in a joint different from that in which CPP arthritis was diagnosed. At the very least, the patient with both crystal types in the same joint – and likely some of the others – could be classified as having mixed crystal disease. Aside from occasional data, little is known about this condition.The formation of MSU crystals is a consequence of hyperuricemia, and at least some of the mechanisms of crystal formation appear similar to those of biomineralization2; other factors likely influence the nucleation of the crystals3. At the joint, MSU crystals form on the surface of the joint cartilage and their passage to and … Address correspondence to Prof. E. Pascual, Universidad Miguel Hernandez, Carretera Nacional 332 s/n, 03550, San Juan de Alicante, Alicante, Spain. E-mail: pascual_eli{at}gva.es ER -