Which protein bands are significant?

CASE DESCRIPTION The serum protein electrophoresis pattern (SPEP) for an 82-year-old female patient with known monoclonal gammopathy of undetermined significance demonstrated 2 aberrant protein bands, one in the 21 interzone (Fig. 1A, fat arrow) and one in the 12 interzone (Fig. 1A, thin arrow). The immunofixation electrophoresis (IFE) (Fig. 1B) revealed a large IgA paraprotein in the 12 interzone (Fig. 1B, thin arrow) but only a very faint IgA heavy-chain paraprotein corresponding to the large 21 interzone band (Fig. 1B, fat arrow).