This Study Aims to Clarify the Prevalence and Characteristics of Neuropathy, Along With Associated Paraclinical Findings in Patients With Waldenström's Macroglobulinemia (WM) in a Cohort of WM Patients to Optimize the Diagnostic Process

Methods Study design: Cross-sectional observations study Outcome: Prevalence: Determining how many WM patients have neuropathy. Characterization: Identification of clinical subtypes of WM associated neuropathy and their symptoms. Biomarkers?Biomarkers Something measurable in the body, such as a blood test result or an imaging finding, that indicates how a condition or treatment is behaving.: Establishing relevant biomarkers (e.g., neurofilament light chain) to diagnose and predict neuropathy outcome. We have already identified all patients with an active diagnosis of Waldenström Macroglobulinemia followed at the Department of Haematology at Rigshospitalet in august 2024. All patients have been screened with a questionnaire designed to identify signs of neuropathy. If probable symptoms of neuropathy the patients will be examined in the Department of Neurology. Almost 600 patients has been invided. 100 patients have symptoms fulfilling the criteria for probable neuropathy. With expect 90 patients patients in total to undergo clinical examination. Neuropathy will be clinically classified and confirmed with a nerve conduction study (ENG). Patient with neuropathy associated to WM will be further investigated with blood samples and lumbar puncture?lumbar puncture A procedure in which a needle is placed between the bones of the lower back to collect spinal fluid or to give a treatment.. The study duration will be one year, where we expect all participants to have gone through questionnaire, clinical examination, nerve conduction study and paraclinical tests. The follow up?follow up The period after treatment or enrolment during which participants are observed or contacted, for example to record side effects or outcomes. period will be for 3 years. Clinical examination will be done by the responsible investigator Morten Müller Aagaard, MD. Methodes include:

• Clinical examination

Neurological examination by a trained physician within the field of neuropathy.

• Nerve conduction study (ENG)

Paraclinical test of the sensory- and motornerves of the peripheral nervous system.

• Questionnaires: I-RODS, FES-I, COMPASS 31, FSS and 5Q-5D
• Blood samples

The blood samples will be analysed with a standard polyneuropathy panel (liver, blood sugar/diabetes, kidney and hematologic markers e.g. interleukin-6, immunoglobulin A, G and M, kappa/lambda-chains and M-protein). Additionally the samples will be analysed for paraneoplastic antibodies, marker of neurodegenerative processes (e.g. neurofilament), rheumatologic markers (SSA, SSB, cryoglobulin, SR), and infection disorders as hepatitis b + c antibodies and HIV. In collaboration with department of immunology we also want to examine samples for complement activity and inflammation markers including cytokines. Whole genome squencing (WGS) for inherited neuropathies.

• Cerebrospinal fluid

Cerebrospinal fluid will be examined with standard tests (erythrocytes, leucocytes, glucose, protein, neurofilament light polypeptide, borrelia, flowcytometry, cytology, and CXCL13) The study duration will be 1 year with extra follow up for 3 years. Statistics The study is designed as a cross-sectional observation study describing WM associated neuropathy. The prevalence of neuropathy associated to WM will be estimated. Non-responders will be classified as missing data at random. In addition, sensitivity analyses will be conducted where the prevalence of neuropathy in non-responders will be varied within reasonable range and combined with information from the responders. Data will be processed using standard descriptive statistics, comparing results with normative reference values. Differences between WM patients and normal material will be analysed using t-tests, with p-values <0.05 considered statistically significant. The types of neuropathies, defined through electrophysiological and clinical phenotypes will undergo subgroup analyses based on group sizes. Statistical differences in clinical outcomes and biomarkers will be examined using ANOVA tests. Impact

• Clinical Understanding

Enhanced Knowledge: The study will improve understanding of the prevalence, types, and pathophysiology of neuropathy associated with WM, leading to better recognition of the condition among healthcare providers. Treatment Guidelines: Establish clinical markers that may contribute to initiating or intensifying treatment for neuropathy associated with WM.

• Patient Management

Improved Diagnosis: Identification of specific biomarkers and clinical indicators will facilitate earlier and more accurate diagnoses of neuropathy, allowing for timely intervention. Optimal Monitoring: Contributing to better surveillance and management of WM regarding development of neuropathy in clinical practice. Tailored Treatments: Insights into which patients are likely to benefit from specific treatments can lead to studies about more personalized and effective treatment strategies.

• Quality of Life

Functional Preservation: Addressing neuropathy early will lead to more rapid interventions both treatment and focus on the disabilities. Thus, patients may experience better maintenance of their mobility and daily functioning, thereby improving their overall quality of life.