<prompt> In pseudogout, material deposited isSodium oxalateCalcium apatiteMonosodium urateCalcium pyrophosphate  <response>: Ans: d calcium pyrophosphate Ref: Harrison 17th edp.2167.In Pseudogout, calcium pyrophosphate is depositedIn Gout, Monosodium urate crystal is depositedAssociations of CPPD calcium pyrophosphate dihvdrate crystal deposition:- Ageing most common Osteoarthritis Familial Metabolic diseases-HaemochromatosisHyperparathyroidismHypophosphatasiaHypomagnesaemiaWilsons diseaseCompensated polarised light microscopy of synovial fluids:-Monosodium urate crystals - Bright birefringence negative sign and needle shaped morphologyCalcium pyrophosphate crystals - Weak birefringence positive sign and rhomboid morphology.Note:-o Osteoarthritis- involvement of PIP, DIP and 1st carpometacarpal joint base of thumb. Sparing of MCP and wrist.o Rheumatoid arthritis - involvement of any small joints of the hand i.e PIP, MCP, and wrist. Sparing of DIP.o Psoriatic arthritis - involvement of PIP, DIP, MCP and wrist. Sparing of any joint may or may not be present. 