Monoclonal gammopathy of undeterminated significance and endoneurial IgG deposition: A case report.
BACKGROUND
Monoclonal gammopathy of undeterminated significance is the most common form of plasma cell dyscrasia, usually considered as benign. In rare cases it may have a malignant course, sometimes limited to an organ such as peripheral nerves.


METHODS
We describe clinical, electrophysiological and pathological findings in a patient presenting a immunoglobulin G (IgG) paraproteinemic polyneuropathy clinically mimicking a chronic inflammatory demyelinating polyneuropathy.


RESULTS
Immuno-electron microscopy (immune-EM) demonstrated that the widenings of the myelin lamellae resulted from the infiltration of IgG between a significant number of myelin lamellae (with absence of inflammatory cells in the epineurium, endoneurium, and perineurium, and the lack signs of vasculitis). This patient was finally treated successfully with lenalidomide then mycophenolate mofetil.


CONCLUSIONS
In polyneuropathies associated to a monoclonal gammopathy, a nerve biopsy may clinch the diagnosis. Immuno-EM may be required to determine the role of the pathological immunoglobulin in the destruction of the peripheral nerve parenchyma. Diagnosis of such a direct involvement of peripheral nerve can endorse more aggressive treatment of real efficiency.
Department of Neurology, Nerve-Muscle Unit, CHU Bordeaux (Groupe hospitalier Pellegrin), Place Amélie Raba-Léon, Bordeaux, France La Casamance Hospital, Aubagne, France European Hospital, Marseille, France Department and Laboratory of Neurology, Centre de Référence 'neuropathies périphériques rares', CHU Limoges, Limoges, France.
Stéphane
S
Mathis
Jérôme
J
Franques
Laurence
L
Richard
Jean-Michel
JM
Vallat
D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D008998:Monoclonal Gammopathy of Undetermined Significance / Q000150:complications*; D010525:Peripheral Nerves / Q000378:metabolism*; D020277:Polyradiculoneuropathy, Chronic Inflammatory Demyelinating / Q000276:immunology* / Q000378:metabolism* / Q000628:therapy
D007074:Immunoglobulin G