Free light chains (FLCs) are tumour markers of monoclonal gammopathies. Detection of urinary FLC or also known as Bence-Jones protein through urinary protein and its immunofixation electrophoreses (UPE and uIFE, respectively) have been considered the gold standard for its biochemical diagnosis. This is mainly due to their superior detection limits compared to their counterpart investigations in serum. However, urinalysis is limited in many ways. The emergence of serum FLC assay with markedly improved detection limit circumvents many of these problems and has gained much importance in biochemical investigations of monoclonal gammopathies. Nevertheless, they are not without limitations. This review discusses the advantages and limitations of serum and urinary FLC assays.
Monoclonal gammopathies result from an overproduction of a single abnormal clone of plasma cell
or B lymphocyte that produce an immunologically homogenous immunoglobulin (Ig) commonly referred to as paraprotein or monoclonal (M) protein. The circulating M-protein may consist of an intact immunoglobulin, the light chain only, or (rarely) the heavy chain only. The heavy chain is from one of the five immunoglobulin classes G, A, M, D or E, while the light chain is either kappa (κ) or lambda (λ) in type. Accurate detection and quantitation of monoclonal immunoglobulins is important for the diagnosis and management of monoclonal gammopathies. We report a case of a 71 year old lady with a history of chronic gastritis and recurrent lower respiratory tract infection whereby no specific diagnosis was made until a computed tomography (CT) guided lung biopsy and orogastroduodenoscopy (OGDS) 5 years later from the onset of initial symptoms revealed pulmonary and gastric amyloidosis, respectively.
Multiple myeloma (MM) is characterized by progressive proliferation of malignant plasma cells, usually initiating in the bone marrow. MM can affect any organ; a total of 7 - 18% of patients with MM demonstrate extramedullary involvement at diagnosis. Non-secretory multiple myeloma (NSMM) is a rare variant that accounts for 1 - 5% of all cases of multiple myeloma. The disease is characterized by the absence of monoclonal gammopathy in serum and urine electrophoresis. Our case report highlights the diagnostic challenge of a case of NSMM with extensive extramedullary involvement in a young female patient who initially presented with right shoulder pain and bilateral breasts lumps. Skeletal survey showed multiple lytic bony lesions. The initial diagnosis was primary breast carcinoma with osseous metastases. No monoclonal gammopathy was found in the serum or urine electrophoresis. Bone marrow and breast biopsies revealed marked plasmacytosis. The diagnosis was delayed for a month in view of the lack of clinical suspicion of multiple myeloma in a young patient and scant biochemical expression of non-secretory type of multiple myeloma.
Plasma cell leukaemia (PCL) is an aggressive haematological malignancy which is classified into primary (pPCL) and secondary PCL. A 39-year-old Indian man presented to the Department of Hematology with a 2-week history of fever and lethargy. Clinically, he was pale and febrile. Haemogram revealed bicytopenia with leucocytosis. The peripheral blood film portrayed rouleax formation with 45% of circulating plasma cells. Serum protein electrophoresis and immunofixation revealed IgG lambda paraproteinaemia of 48 g/L. Bone marrow aspirate, flow cytometry and trephine were consistent with IgG lambda pPCL. He was treated with six cycles of bortezomib, thalidomide and dexamethasone combination chemotherapy followed by high-dose melphalan conditioning and autologous stem cell transplant. Currently, he is in complete remission for the past 18 months and is on oral lenalidomide maintenance therapy. Prognosis is often dismal in pPCL with the median overall survival below 1 year if treatment is delayed.