Atypical IgA with hidden light chain.

A 64-year-old Caucasian male was examined following complaints of persistent malaise and fatigue. Electrophoretic analysis of the patient's serum revealed a paraprotein spike which was initially attributed to α chains. However, subsequent reduction and alkylation of the purified protein showed the presence of free light chains of κ type. Further proof of the κ type light chains was obtained from tests with antisera to the paraprotein. This case represents another instance of a `hidden' light chain in a paraprotein, possibly related to the tertiary structure and not a case of α-chain disease as initially thought.