Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an immune-mediated, acquired polyneuropathy affecting spinal nerve roots and peripheral nerves, typically progressive or relapsing-remitting. Diagnosis can be challenging due to strict criteria and confounding comorbidities, especially with the growing range of CIDP variants and CIDP-like neuropathies. This case highlights a patient with chronic inflammatory neuropathy and multiple comorbidities that likely contributed to her condition.

A 52-year-old woman with history of type-1 diabetes, hypothyroidism, hemolytic anemia and breast cancer (treated with carboplatin, paclitaxel and pembrolizumab) presented to the neuromuscular clinic in mid-2023 with difficulty walking and leg pain for 4 months, bilateral foot numbness since 2020, and foot drop starting in mid-2022.

Nerve conduction studies (NCS) and electromyogram (EMG) demonstrated a chronic, generalized, moderately severe axonal > demyelinating sensorimotor peripheral polyneuropathy. Due to demyelinating features on EMG, a neuromuscular ultrasound (NMUS) was conducted, revealing marked multifocal enlargement of the median and ulnar nerves, and brachial plexus trunks at both entrapment and non-entrapment sites.

Lumbar puncture showed profound albuminocytologic dissociation. IVIG was initiated, resulting in clinical improvement with patient being discharged on maintenance IVIG every 3 weeks. Unfortunately, her diabetes and hypothyroidism became uncontrolled for several months post-hospitalization. She subsequently tested borderline positive for Caspr-1 antibodies, raising concerns for an alternative diagnosis of autoimmune nodo-paranodopathy. However, sural nerve biopsy showed diffuse loss of large and small myelinated axons with C5b-9 expression in endoneurial microvasculature, with no signs of vasculitis or active demyelination. A follow-up NMUS in March 2024 evaluated the response to IVIG, demonstrated reduced or normalized nerve size at some sites, despite clinical and electrophysiologic decline.

Ultrasound showing reduced or normalized nerve size has been reported in response to successful CIDP treatment. This case illustrates an ultrasound response to IVIG treatment in a chronic inflammatory neuropathy, despite confounding comorbidities limiting clinical improvement.