A pediatric case of multifocal motor neuropathy with the conduction block

Background: Multifocal motor neuropathy with conduction block (MMNCB) is a rare immune-mediated motor neuropathy, predominantly seen in adults, with few pediatric cases reported. It presents as asymmetric distal limb weakness without sensory loss. Diagnosis is based on clinical features, nerve conduction studies (NCS), and occasionally anti-ganglioside antibodies, which are less frequently positive in children. Intravenous immunoglobulins (IVIG) are the primary treatment, with corticosteroids and plasmapheresis being ineffective. Case presentation: We report the case of a 14-year-old boy presenting with progressive, asymmetric limb weakness over one year, beginning with the left foot and later involving all limbs. The weakness affected distal muscles more severely, impairing his mobility and daily activities. Neurological examination revealed reduced muscle tone, generalized areflexia, and preserved sensory function. NCS demonstrated conduction block with temporal dispersion in multiple motor nerves, consistent with MMNCB. Anti-GM1 antibodies were negative, but anti-GM3 and GD1b antibodies were positive. Cerebrospinal fluid analysis showed elevated protein levels without pleocytosis. The patient was treated with IVIG (0.4 g/kg/day for five days) and initiated on occupational and physiotherapy. Significant improvement in muscle strength was observed within three months, with only mild residual weakness. Conclusion: This rare case highlights the diagnostic challenges of MMNCB in pediatric patients and highlights the importance of clinical and electrophysiological correlation, even in the absence of anti-GM1 antibodies. Early recognition and timely IVIG therapy can lead to remarkable recovery, emphasizing the need for increased awareness of this rare pediatric condition.