SERPING1 and monoclonal gammopathy: This condition is primarily associated with lymphoma and monoclonal gammopathy.[6–8] Some cases are described with cancer or autoimmune conditions [7,8]; in approximately 15% of cases, no associated condition was identified.[7] A decrease of the functional C1INH level <50% of the reference value is commonly used to define the disease.[7,9] Decreased levels of C4 and CH50 are regularly observed.