This prospective longitudinal study will follow participants with Multifocal Motor Neuropathy over time and collect data on their clinical outcomes, quality of life, and use of health care resources. Participants will follow their regular visit schedule with their treating physician, except for an optional second visit occurring 7 to 14 days after the start of the study to collect biomarker data. No IMP will be administered.

Inclusion Criteria:

• Is at least the local legal age of consent for clinical studies when signing the ICF
• Is capable of providing signed informed consent and complying with protocol requirements
• Has an existing or new diagnosis of MMN made by a neuromuscular specialist or neurologist

Exclusion Criteria:

• Is currently participating in any clinical study with an IMP
• Has other medical conditions that could affect the assessment of MMN

Patients with MMN receiving standard of care at their treating physician.