(Kiosk 4) Ultrasound Identification of Seronegative Treatment-responsive Distal Acquired Demyelinating Symmetric Neuropathy: A Case Study

Case Diagnosis: Distal acquired demyelinating symmetric (DADS) neuropathy

Case Description: A 63-year-old female presented after 1 year of pain, numbness, and tingling in her feet and 4 months of similar symptoms in her fingers. She also noted lower extremity weakness and balance impairment. No proximal weakness, cranial nerve deficits, or sphincter dysfunction were noted. Electrodiagnostic studies showed dramatic distal conduction slowing and temporal dispersion, and neuromuscular ultrasound revealed diffuse nerve enlargement in non-entrapment sites in the upper and lower extremities. Bloodwork revealed no monoclonal gammopathy or anti-myelin-associated glycoprotein (anti-MAG) antibodies. A lumbar puncture showed markedly elevated CSF protein without increased cell count. The patient began intravenous immunoglobulin (IVIg) treatment, which was well tolerated and improved symptoms significantly.

Discussion: DADS neuropathy is a rare condition with notable heterogeneity in presentation. Affected patients are predominantly male, and about two-thirds of patients test positive for M-protein and anti-MAG antibodies. Patients often do not respond to IVIg treatment, although seronegative patients are more likely to respond. Neuromuscular ultrasound is not used in many centers to assist in diagnosis of DADS neuropathy. Our case provides an example of a female, seronegative DADS patient with diffuse nerve enlargement on neuromuscular ultrasound who responded well to IVIg treatment. This case deepens the understanding of the clinical picture of M-protein-negative DADS neuropathy and argues for the increased role of neuromuscular ultrasound in diagnosis.

Setting: Neuromuscular practice

Assessment/Results: The patient continues to tolerate IVIg after 2 years of treatment. She remains asymptomatic on a regimen of IVIg every 3 weeks.

Conclusion: DADS neuropathy is a rare condition that can present with a variety of clinical findings. In seronegative cases in particular, awareness of the specific clinical and electrodiagnostic presentation and finding of diffuse nerve enlargement on neuromuscular ultrasound can facilitate diagnosis at an early and potentially IVIg responsive stage.