Monoclonal gammopathy of undetermined significance (MGUS) occurs in 3-7% of the elderly population, with higher prevalence in renal failure patients, and is associated with a 25-fold increased lifetime risk for plasma cell myeloma (PCM), also known as multiple myeloma. Using the California State Inpatient, Emergency Department, and Ambulatory Surgery Databases components of the Healthcare Cost and Utilization Project (HCUP), we sought to determine if patients with MGUS who undergo solid organ allograft (n=22,062) are at increased adjusted relative risk (aRR) for hematological malignancy and other complications. Among solid organ transplant patients, patients with preexisting MGUS had higher aRR of PCM (aRR 19.46; 95%CI 7.05, 53.73; p<0.001), venous thromboembolic events (aRR 1.66; 95%CI 1.15, 2.41; p=0.007), and infection (aRR 1.24; 95%CI 1.06, 1.45; p=0.007). However, when comparing MGUS patients with and without solid organ transplant, there was decreased aRR for PCM with transplant (aRR 0.34; 95%CI 0.13, 0.88; p=0.027), and increased venous thromboembolic events (aRR 2.33; 95%CI 1.58, 3.44; p<0.001) and infectious risks, (aRR 1.44; 95%CI 1.23, 1.70; p<0.001). While MGUS increased the risk of PCM overall following solid organ transplantation, there was lower
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