Septic arthritis, gout, pseudogout and osteoarthritis in the knee of a patient with multiple myeloma

This report describes a 79‐year‐old Negro woman with multiple myeloma in whom a pneumococcal infection occurred in a previously asymptomatic but severely osteoarthritic knee. Treatment with penicillin was associated with rapid partial resolution of the inflammation. Synovial fluid cultures initially contained a Type 22 pneumococcus but were negative after the first hospital day. On the eleventh hospital day, synovial aspirate revealed intra‐ and extracellular crystals not previously present. There were crystals with strong negative birefringence, digestible by uricase, which were morphologically typical of monosodium urate crystals. Also present were many monoclinic and triclinic crystals with weak positive birefringence, morphologically typical of calcium pyrophosphate dihydrate. This patient's clinical course was consistent with the possibility that enzymes, released during the early septic process, digested cartilage matrix, releasing, into the joint space, crystals that had been deposited previously in a protected intracartilagenous site.