Introduction

Amyloid light chain (AL) amyloidosis is a plasma cell (PC) disorder characterised by the overproduction of monoclonal immunoglobulin light chains (LC). It can be treated effectively with chemotherapy with or without stem cell transplantation, proteasome inhibitors or immunomodulatory drugs.

Diagnosing AL amyloidosis requires the detection of tissue amyloid deposits in association with monoclonal immunoglobulin LC production, which can be detected by serum or urine immunofixation electrophoresis (S/UIFE), serum free light chain (FLC) assay and/or bone marrow assessment of clonal PCs.1 ,2 In some clinical circumstances, it may be necessary to prove the monoclonal LC nature of the amyloid using immunoelectron microscopy or mass spectrometry.3

The current modalities to demonstrate the clonality of amyloidogenic PCs in the bone marrow include flow cytometry, immunohistochemistry (IHC) and in situ hybridisation (ISH). Owing to the small volume of the PC population in AL amyloidosis, however, detection of clonal PCs is often difficult.4 ,5

Cyclin D dysregulation has been proposed to be a common mechanism in PC disorders, as in multiple myeloma; the majority of patients have dysregulated cyclin D expression.6 This has not been extensively investigated in AL amyloidosis. In this study, we evaluated cyclin D1, D2 and D3 protein expression in AL amyloidosis, and compared cyclin D positivity to other conventional laboratory parameters as a diagnostic tool and as a potential biomarker for minimal residual disease.