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

Multifocal motor neuropathy with conduction block (MMNCB) is a rare acquired immune-mediated demyelinating neuropathy that affects peripheral motor nerves, presenting as asymmetric, usually upper limb weakness without sensory impairment. Its concurrence with non-Hodgkin lymphoma (NHL) is an exceedingly rare phenomenon. This case describes a patient who presented with sequential bilateral foot drop starting from the left foot, with an ensuing weak hand grip. She was discovered to have cervical and occipital lymphadenopathy, which occasioned further blood work and tissue diagnosis. Her electrodiagnostic studies showed multiple asymmetric motor conduction blocks, normal distal motor latencies, and sensory studies consistent with a diagnosis of MMNCB. Her lymph node biopsy revealed diffuse large B-cell lymphoma (DLBCL). She could not afford intravenous immunoglobulin (IVIG); hence, pulse intravenous methylprednisolone was tried with no response. While her blood work showed a new diagnosis of HIV infection, her antiganglioside antibody panel was negative for anti-GM1 antibodies. Fortunately, her weakness began to improve in the third month of her chemotherapy with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone (R-CHOP). Case reports have only provided the association of MMNCB and lymphoma. How each condition influences the other's manifestation, treatment, and prognosis is still poorly understood.