The anti-myelin-associated glycoprotein (anti-MAG) syndrome may develop in patients with an IgM monoclonal gammopathy. MAG is a glycoprotein that is a component of the myelin sheath around peripheral nerves.


Clinical features:

(1) IgM monoclonal gammopathy, often as MGUS but occasionally with Waldenstrom's macroglobulinemia

(2) elderly patient

(3) typically male (3:1 or 4:1 male to female ratio)

(4) presence of a distal neuropathy that is slowly progressive over years with functional disability

(4a) may start as mild paresthesias

(4b) sensory loss in distal lower limbs with gait and balance disturbances

(4c) may develop a sensory loss in the upper limbs

(4d) variable motor weakness which can result in distal wasting, foot drop, and difficulties in ambulation

(4e) intention tremor may be present

(4f) gait ataxia may be present

(5) antibody to myelin-associated glycoprotein (anti-MAG) present (titers > 1:6.400 are considered high titered and from 1:200 to 1:6,400 as low titered)

(6) elevated CSF protein (> 100 mg/dL) with low cellularity

(7) abnormal electrodiagnostic studies with:

(7a) demyelinating pattern with reduced nerve conduction

(7b) prolonged F-wave latency

(7c) marked prolongation of the distal motor latencies in comparison to proximal segment conduction velocities

(8) nerve biopsy shows segmental demyelination with deposits of IgM and complement on myelin sheaths


NOTE: This might be classified as a paraneoplastic syndrome in a patient with Waldenstrom's macroglobulinemia.


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