Anti-Neutrophil Cytoplasmic Antibody (ANCA)-Associated Vasculitis Manifesting Solely as Bilateral Toe Cyanosis: Case-Based Review

Background Blue toe syndrome (BTS) is characterized by an acute onset of often painful and blue/violaceous discoloration of the toes due to impaired blood flow, leading to ischemia.[1] The etiology of BTS is broad, therefore a careful history, physical examination, and investigations are essential. Herein, we present what we believe to be the first documented case of BTS as the sole manifestation of PR3-ANCA-associated vasculitis (Figure 1). While there is 1 other reported case, that instance differed as it progressed to mononeuritis multiplex and renal impairment.[2] Our case remained distinctively singular in its presentation, with no involvement of other organs, which highlights the rarity and significance of our findings. Fig. 1 This figure illustrates blue toe syndrome in a patient with PR3-ANCA vasculitis, as described in the case report. Figure A shows the blistering episode on the right second toe, while Figures B and C depict bilateral toe cyanosis. All photos were taken before initiating treatment with azathioprine. This figure was generated using BioRender. Case A 71-year-old East-Asian female presented with a 2-year history of constant bilateral cyanosis of all toes, not influenced by temperature changes. These symptoms preceded the COVID-19 pandemic. She denied finger involvement, erythromelalgia, or other rashes. There were no signs of ANCA-associated vasculitis. She had tried ASA 81mg without improvement and nifedipine 30mg with mild relief before seeking rheumatological evaluation. Laboratory investigations were remarkable for positive c-ANCA with a titer PR3 of 735 mean fluorescence units. Other rheumatologic investigations, including antinuclear antibody, extractable nuclear antigens, rheumatoid factor, anti-cyclic citrullinated peptide, anti-double stranded DNA, scleroderma panel, and anti-phospholipid antibodies, were negative. Uveitis/interstitial lung disease were ruled out and general chemistry parameters were normal. She was found to have Type III cryoglobulinemia and hematology was consulted for a full workup of her positive cryoglobulins, which were all unremarkable. There were no signs of connective tissue disease or hepatitis infection. Azathioprine was started and she was seen in follow-up a year later with a significant decrease in cyanosis of her toes and a decrease in PR3 tire to 3.7. Conclusion In this report, we identify, to the best of our knowledge, the first documented case of PR3-ANCA vasculitis presenting with BTS as the sole and primary manifestation. Since the patient had positive cryoglobulins, and cryoglobulins can precipitate at temperatures as high as 36°C, the diagnosis was considered; however, her symptoms did not fluctuate with temperature changes. Furthermore, mixed cryoglobulinemia is usually supported by an elevated rheumatoid factor, which was not evident in this case.[3] We believe the patient to be asymptomatic concerning the cryoglobulins which aligns with literature encouraging clinicians to separate those with low detectable levels of cryoglobulins from those with the actual disease state of “cryoglobulinemia”.[3] [1.] Hirschmann JV. J Am Acad Dermatol 2009;60:1-20. [2.] Marinchev L. Open Med 2013;8:577-9. [3.] Dispenzieri A. Curr Treat Options Oncol 2000;1:105-18.

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