Randa A. Nimeri MRCP, MSc, MD 1, Boardman Jeremy MD 2
1. Consultant Clinical Neurophysiologist, Royal Preston Hospital Medical, UK
2. Consultant Neurologist, Royal Preston Hospital Medical, UK

Abstract

Introduction: In patients with anti MAG  neuropathy, IgM antibodies react with Schwann cell glycoproteins, including MAG and peripheral myelin protein 22 (PMP22).  This reaction makes the nerves liable to entrapment at the common entrapment sites due to loss of PMP22 function and anti- MAG antibodies; and it may cause increased sensitivity to nerve entrapment.

Methods: This is a case of a young patient with progressive lower limb sensory disturbance and mild balance disturbance. His neurophysiology showed evidence of neuropathy with subclinical entrapment neuropathies across the wrists ,elbows and around the fibular neck bilaterally. His bloods showed monoclonal gammopathy of uncertain significance (MGUS) and abnormal anti MAG antibodies.

Results: Our patient is 47-year-old male, presenting with progressive lower limb sensory disturbances over four years. He has a family history of bilateral pes planus. His balance deteriorated due to reduced proprioception significantly impacting activities such as walking and climbing ladders. On examination he had muscle wasting in his feet, absent reflexes except at the knees, mild dorsiflexion weakness, and sensory deficits to pinprick and proprioception. Nerve conduction studies confirmed significant neuropathy with demyelinating features in the lower limbs, alongside evidence of subclinical nerve entrapment of the median nerves across the wrists, ulnar nerves across elbows, and common peroneal nerve at the fibular neck bilaterally. Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) was suspected, but genetic testing for the PMP22 deletion was negative. In addition, protein electrophoresis revealed an IgM lambda band of 3.7 g/L, suggesting a monoclonal gammopathy of uncertain significance. Given his family history of pes planus and the presence of a monoclonal IgM band, possible etiologies included mild genetic neuropathy, immune-mediated processes, or paraproteinemic neuropathy suspected. Further hematological evaluation were performed. His Anti MAG antibody was abnormal. This suggested Anti MAG neuropathy.

Conclusion: This case underscores the importance of evaluating hereditary, autoimmune, and hematological contributions to chronic sensorimotor neuropathy. In addition, Hereditary Neuropathy with Liability to Pressure Palsies might mimic the presentation of chronic autoimmune neuropathy, especially early in their clinical presentation, of anti-myelin associated glycoprotein neuropathy. This is because the IgM antibodies react in the peripheral myelin protein 22.  This reaction makes the nerves liable to entrapment at the common entrapment sites due to loss of PMP22 function.