To describe a case of microscopic polyangiitis (MPA) presenting as a subacute ascending symmetric neuropathy, mimicking chronic inflammatory demyelinating polyneuropathy (CIDP).

Neuropathy is present in about half of MPA cases. It usually presents as a painful mononeuritis or mononeuritis multiplex with other neurologic or prior long-standing systemic manifestations. 

Case Presentation: A 69 year-old male with type II diabetes, congestive heart failure, and pulmonary hypertension presented with a 5-month history of ascending symmetric numbness and weakness in his lower extremities and more recently his bilateral hands, requiring a walker for ambulation. His neurological exam was notable for distal>proximal symmetric upper and lower extremity weakness, a length-dependent symmetric decrease in pinprick, vibration, and proprioception in his upper and lower extremities, and diffuse hyporeflexia. His initial serum work up was notable for a leukocytosis of 13, erythrocyte sedimentation rate of 59, and c-reactive protein of 15.1 with a co-occurring symptomatic urinary tract infection. His creatinine was 1.51 with concomitant hyponatremia and proteinuria, thought to be secondary to cardiorenal syndrome or diabetic chronic kidney disease.  His cerebrospinal fluid (CSF) studies were unremarkable, including a protein of 28 and white blood cell count of 3. Contrasted magnetic resonance imaging of his cervical- and lumbar-spine were unrevealing. His antineutrophil cytoplasmic antibodies (ANCA) vasculitis panel resulted with a titer of 1:640 with a perinuclear-ANCA pattern, with a Myeloperoxidase IgG of168. Electromyography and nerve conduction studies (EMG/NCS) showed a severe bilateral axonal sensorimotor polyneuropathy with some asymmetric features. Nerve and renal biopsy both showed vascular lymphocytic infiltration, confirming the diagnosis.

Vasculitic neuropathies can present as CIDP-mimics. While usually asymmetric and accompanied by other systemic findings, vasculitis can present with subacute symmetric ascending numbness and weakness, with other systemic manifestations found thereafter. Results from EMG/NCS, CSF studies, and nerve biopsy can help distinguish between CIDP and vasculitis.