FREE FRAGMENTS OF GAMMA-CHAIN IN THE URINE - POSSIBLE SOURCE OF CONFUSION WITH GAMMA-HEAVY-CHAIN DISEASE

With currently used microconcentrators, high-resolution electrophoresi s, and immunofixation electrophoresis, relatively homogenous free frag ments of gamma chain (FFGC) unaccompanied by light chains, which canno t be found in the serum, may be discovered in the alpha-2 region durin g routine examination of the urine. The urinary alpha-migrating FFGC i s of no apparent clinical significance and should not be confused with the antigenically related FFGCs of gamma heavy-chain disease. In gamm a heavy-chain disease, the FFGCs are often demonstrable in the urine, but are always present in the serum and migrate in the beta-gamma regi on.