Lewis—Sumner syndrome: a case report

Lewis—Sumner syndrome (LSS), also known as multifocal acquired demyelinating sensory and motor neuropathy (MADSAM), is a rare variant of chronic inflammatory demyelinating polyneuropathy (CIDP) characterized by asymmetric, focal involvement of peripheral nerves. This immune-mediated disorder typically follows a slowly progressive course and may significantly impair patients’ working capacity, functional activity, and quality of life. The clinical presentation of LSS includes gradually increasing asymmetric weakness in both distal and proximal segments of the limbs, sensory disturbances such as paresthesias, numbness, or pain, and reduction or loss of tendon reflexes, which complicates early recognition of the condition. The multifocal and asymmetric pattern of symptoms often leads to misdiagnosis as mononeuropathy, plexopathy, or radiculopathy, delaying the establishment of the correct diagnosis. A crucial step is the differentiation of LSS from multifocal motor neuropathy, vasculitic neuropathies, and classical CIDP, as treatment strategies differ substantially. This article presents a clinical case that illustrates the typical diagnostic challenges and emphasizes the pivotal role of neurophysiological testing. Electroneuromyography (ENMG) is indispensable, as it enables the detection of conduction blocks, temporal dispersion, slowed conduction velocities, and provides objective confirmation of the demyelinating nature of nerve involvement. ENMG findings ensure accurate diagnostic verification, localization, assessment of disease severity, and facilitate dynamic monitoring of treatment response. The integration of clinical examination, laboratory testing, and neurophysiological studies ensures the highest diagnostic accuracy and facilitates the development of an evidence-based treatment strategy. Current treatment strategies include the use of intravenous immunoglobulins, corticosteroids, plasma exchange, and immunosuppressants, which can achieve sustained clinical improvement and reduce the risk of disability. The aim of this publication is to increase awareness and vigilance among clinicians regarding this rare and diagnostically challenging disease, which requires a multidisciplinary approach. Timely diagnosis, early initiation of immunotherapy, and individualized management significantly influence prognosis and improve patients’ quality of life.