Case Presentation: A 65 year-old female with past medical history of type 1 diabetes mellitus, renal transplant, breast cancer, sarcoidosis, and hypothyroidism presented with acute onset of severe pain, numbness, and weakness of bilateral upper and lower extremities. The patient developed rapidly progressive fatigue and weakness over three days following acute bronchitis six weeks prior. Vital signs were within normal limits. Her physical exam was notable for absent sensation distal to the ankles bilaterally; 1/5 strength in dorsiflexion of the left foot, flexion of bilateral metatarsals, and flexion of bilateral wrists; and 3/5 strength with wrist extension bilaterally. She additionally had diffuse, non-tender ecchymoses distally on each extremity. Review of systems was positive for diffuse myalgias. Laboratory tests showed ESR 78 mm/hr, CRP 15 mg/dl, CK 84 U/L, RF 19 U/mL, anti-ccp 159 U/mL, anti-MPO 38.7 U/mL and p-anca titer of >1:640. The creatinine on admission was baseline at 1.50 mg/dl. Urinalysis showed mild proteinuria and microscopic hematuria. MRI of the brain and spine were negative for acute changes and CT Chest Abdomen Pelvis showed no masses. Biopsy of the transplanted kidney showed pauci-immune, necrotizing crescentic glomerulonephritis and segmental fibrinoid necrosis. With biopsy findings, clinical progression and symptoms, elevated inflammatory markers, and positive p-anca, the patient was diagnosed with ANCA-associated vasculitis (AAV), specifically microscopic polyangiitis (MPA). She was given pulse dose steroids and ultimately initiated on rituximab prior to discharge to inpatient rehab.

Discussion: This case describes isolated peripheral neuropathy as an atypical initial presentation of AAV that clinicians should be aware of. AAV is a rare but increasingly prevalent disease with as many as 421 cases per million.1 AAV affects small to medium sized vessels with three different clinical syndromes. MPA, one of three syndromes, is a pauci-immune necrotizing vasculitis, predominantly affecting small vessels. MPA involves many organ systems including kidneys, musculoskeletal, and lungs most commonly. Peripheral neuropathy is a less common initial presentation with rates varying from 7-58%, and peripheral neuropathy without kidney nor lung involvement at presentation occurs in as few as 9% of patients. 2 While peripheral neuropathies are a rarer presentation of AAV, understanding related characteristics may be helpful to clinicians. Mononeuritis multiplex is the most frequent clinical subtype of peripheral neuropathy in all primary vasculitides, affecting around two-thirds of the patients with peripheral neuropathy. Mononeuritis multiplex describes neuropathy of multiple individual nerves caused by nerve infarctions. Treatment for active disease in AAV includes pulse dose steroids followed by steroid taper with supplementation of immunosuppressing medications. Rituximab-based regimens, as studied in the RAVE trial, have been shown to be more efficacious than the cyclophosphamide-based regimen for inducing remission. 4 Of note, peripheral neuropathy in AAV is associated with higher baseline disease activity,5 but an approach specific for peripheral neuropathy has not been established.6

Conclusions: Clinicians should be aware of peripheral neuropathy, without renal or pulmonary involvement, as a presentation of AAV; especially given earlier diagnosis and subsequently decreased vascular damage is associated with better patient outcomes. 7