Acute demyelinating sensorimotor polyneuropathy in B‐cell lymphoma with IGM autoantibodies against glycolipid GD1B

We report the case of an acute demyelinating sensorimotor polyneuropathy in a patient with IgM autoantibody against peripheral nerve myelin glycolipid GD1b produced by a B‐cell lymphoma. A 76‐year‐old woman presented with one month history of weight loss, paresthesias at the distal extremities of the four limbs followed by progressive and diffuse motor weakness. Neurological examination showed sensory ataxia, marked motor deficit (4 at MRC scale in proximal and distal muscle districts of limbs), superficial and proprioceptive sensory deficit with a stocking‐glove distribution, areflexia at lower limbs. Electroneurography documented absent sensory action potentials, prolonged distal latencies of motor action potentials, markedly slowed motor conduction velocities and evidence of conduction block and temporal dispersion of motor action potentials. Diagnosis of acute demyelinating sensorimotor polyneuropathy was established. CSF examination showed a slight increase of protein concentration. Haematological screening revealed a monoclonal gammopathy with high serum IgM (1151 mg/dL) and light chain kappa proteinuria. A total body CT scan evidenced a pelvic mass identified as low grade B‐cell lymphoma by rectal biopsy. Research for antiganglioside autoantibodies evidenced the presence of IgM antibodies against glycolipid GD1b. Autoantibodies anti‐Mag, anti‐Hu, anti‐Yo and anti‐Ri were negative. The pathogenetic role of serum autoantibodies against glycolipid GD1b in the development of demyelinization in the peripheral nervous system has already been documented either clinically in post‐infective polyneuropathies or experimentally in animal research. This is the first report of selective positivity of anti‐GD1b in polyneuropathy associated to B‐cell lymphoma supporting the possible paraneoplastic significance of these serum autoantibodies.