What is PDN?
Monoclonal Gammopathy, related disorders, MGUS.
MONOCLONAL GAMMOPATHY.Monoclonal means a single clone/copy of a plasma cell. Gammopathy stands for gammaglobulin, another name for antibody or protein. So monoclonal gammopathy is the presence in the blood of a large quantity of one antibody/protein - or paraprotein. The excess protein may be detected as part of any complete physical examination, through a process known as serum protein electropheresis performed on a blood sample. Neurologists are aware that there may be anti-nerve components in the protein that, in certain circumstances, may recognise components on the myelin or axon and react. Thus damage to the myelin and/or the axon of peripheral nerve cells occurs. Most people with a paraprotein in their serum will be unaware of its presence however. It may exist benignly for years without the bearer having any awareness of it or any symptoms of damage ever occurring. Yet some 3% of people with a paraprotein or monoclonal gammopathy may acquire a neuropathy.
POSSIBLE DISORDERSfrom a monoclonal gammopathy. A number of disorders termed paraproteinaemic neuropathies, closely connected with the presence of paraprotein/monoclonal gammopathy, do occur. Peripheral neuropathy (disorder of the peripheral nerves) in association with a monoclonal gammopathy (paraprotein) is not totally uncommon. One group of neurological researchers (Kelly et al) found a paraprotein in 10% of people with otherwise undiagnosed peripheral neuropathies. Systemic diseases such as diabetes mellitus, alcoholism and connective tissue disorders may have been eliminated at an early diagnostic stage.
Most monoclonal gammopathies are non-malignant but when paraprotein is found in the serum along with a neuropathy, then there should be tests for any suspected, potentially serious malignant conditions, in order to exclude them from the diagnosis. These disorders include multiple myeloma, amyloidosis (AL), lymphoma, POEMS syndrome (osteosclerotic myeloma), leukemia and Waldenström's Macroglobulemia. However in 2-3rds of patients with paraprotein and a neuropathy no underlying malignant disorder is found to explain the presence of the monoclonal gammopathy/paraprotein.
MGUS - monoclonal gammopathy of undetermined significance,is then the diagnosis by elimination. There is a smaller amount of paraprotein in the serum of MGUS bearers than in the serum of those with the malignant disorders. Patients with MGUS usually have less than 15% marrow plasma cells; a serum monoclonal protein level less than 3 g/dL. In IgM it is usually <2.5g/dl, in IgA <1.5g/dl and in IgG <2.5g/dl. Also the levels of the other immunoglobulins are within the normal reference range, there is no urinary Bence-Jones protein, and no anemia, renal failure, lytic bone lesions or hypercalcemia. NOTE. The term 'undetermined significance' may be ultimately misleading. It has been assessed that 17% to 25% of MGUS bearers may develop one of the malignant disorders, usually in another ten years.
BY DEDUCTION, if there is an unexplained underlying neuropathywith the MGUS/paraprotein, then the probable remaining form of paraprotein-related polyneuropathy is one of the Paraproteinaemic Demyelinating Neuropathy group – be it IgM, IgG or IgA. These are explained on the next page!
ANNUAL TESTS RE POTENTIAL MALIGNANCY.The level of paraprotein in the blood of every PDN sufferer should be checked at least annually and indefinitely. This is to check for any significant rise in the level that would indicate the developing presence of a more serious malignant condition. However, in a long-term clinical and neurophysiological follow-up of 50 patients "with peripheral neuropathy associated with benign monoclonal gammopathy", that is PDN, only three patients developed haematological malignancy. (Sawantha Ponsford et al. 2000.)
Please note. These notes are based solely on my own experience and my layman's reading of published professional neurology material. They should not be understood as coming from any personal medical expertise. Should any professional neurologist, or anyone else for that matter, spot a terrible error please inform me!