Lymphoma-Associated Multifocal Motor Neuropathy With Conduction Block in a Patient Recently Diagnosed With HIV

Lymphoma-Associated Multifocal Motor Neuropathy With Conduction Block in a Patient Recently Diagnosed With HIV

An Uncommon Neurological Presentation of an Overlapping Immunologic and Oncologic Process

In clinical practice, multifocal motor neuropathy (MMN) is a rare, immune-mediated peripheral nerve disorder characterized by asymmetric distal weakness and electrophysiological evidence of conduction block—typically without significant sensory involvement. It is most commonly idiopathic, but recent literature underscores its association with other immune dysregulations, including malignancy.

A recent case report in Cureus highlights a highly unusual clinical scenario: a 58-year-old man newly diagnosed with HIV, who presented with rapidly progressive bilateral upper-limb weakness, particularly affecting fine motor skills. Nerve conduction studies revealed conduction block in multiple motor nerves—a hallmark of MMN.

However, what makes this case clinically significant is not just the neuropathy—but its underlying cause. Imaging and biopsy ultimately revealed diffuse large B-cell lymphoma (DLBCL), making this a rare case of lymphoma-associated MMN in an HIV-positive patient.

Clinical Pearls from the Case

1. Atypical Neuropathy in HIV Requires a Broad Differential

HIV is well known to cause a spectrum of neuropathies—most commonly distal symmetric polyneuropathy and inflammatory demyelinating polyneuropathies. However, asymmetric motor neuropathy with minimal sensory involvement—as seen in MMN—is uncommon and should raise red flags for paraneoplastic syndromes or coexisting autoimmune processes.

2. Conduction Block Is a Key Diagnostic Clue

The presence of conduction block on nerve conduction studies is not only a diagnostic marker for MMN, but also a therapeutic window. Patients with this pattern often respond favorably to IVIg therapy, as was seen in this case. Timely electrodiagnostic evaluation is therefore critical.

3. Paraneoplastic MMN Should Prompt Malignancy Workup

While rare, paraneoplastic MMN has been reported in association with lymphomas and other hematologic malignancies. The dual presence of HIV and lymphoma can create a complex interplay of immune dysregulation that accelerates neurological involvement. Clinicians must have a low threshold to order imaging, PET scans, and biopsy when MMN is suspected in immunocompromised patients.

 Therapeutic Takeaways

• IVIg remains first-line treatment for MMN with conduction block, regardless of underlying etiology.

• Early intervention may reverse conduction block and restore motor function.

• In lymphoma-associated MMN, treatment of the malignancy is essential for long-term remission and neurologic recovery.

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In this case, the patient improved following initiation of IVIg therapy and was referred for oncology care to begin systemic lymphoma treatment. This underlines the importance of interdisciplinary collaboration between neurology, oncology, and infectious disease.

This case exemplifies how neurologic symptoms can be the first sign of a deeper systemic disease—in this case, a hidden lymphoma in a newly diagnosed HIV patient. MMN with conduction block is treatable—but only if identified early.

For physicians, especially in primary care, neurology, or infectious disease, it's crucial to remember:

When faced with asymmetric motor neuropathy in an HIV-positive patient, think beyond the virus—consider malignancy.

Timely recognition and treatment may not only restore function but potentially uncover life-threatening disease at a treatable stage.