KRT4 and plasma cell myeloma: The protein contains a total of eight aa mutations (S29N, K30R, P40L, Q89H, T94H, Y96Q, S97T and I106L) relative to a homologous 114-residue κ4 Ig VL, LEN, that differs from the germline κ4 sequence at a single position (N29S) but is non-amyloidogenic in vivo, having been extracted as a Bence-Jones protein from a multiple myeloma patient with no symptoms of renal dysfunction or AL amyloidosis7.