In October 2020, a 29-year-old Chinese woman presented to our outpatient department with skin ulcers of the lower limbs and was admitted to our hospital. The patient had a history of recurrent skin ulcers for over 5 years. She had no chronic diseases such as hypertension, diabetes, heart disease, tuberculosis infection, or tumor. According to previous medical reports, ANCA, anti-extracted nuclear antigens (ENA) autoantibodies, anti-double-stranded DNA (dsDNA) antibodies, and antinuclear antibodies (ANA) were negative. Moreover, skin biopsy results revealed that there were a lot of neutrophil infiltration and fibrin deposition in the injured blood vessels, which confirmed the diagnosis of CLV. Unfortunately, we could not trace it back to the original image.
She was initially on MTX (10 mg per os [po, oral route] once a week) for half a year; however, it was ineffective. Colchicine (0.1 g po three times daily) was discontinued after 1 week due to severe gastrointestinal reactions. The patient was then placed on azathioprine (50 mg po twice daily), which was discontinued after approximately 1 month due to adverse effects of myelosuppression. TGTs (20 mg po three times daily) were prescribed and stopped 2 months later because of abnormal menstruation. Contrarily, thalidomide and mycophenolate mofetil were not recommended because she desired subsequent conception. The patient refused these injections and biological agents were not used. Before visiting our department, she accepted prednisone (25 mg po daily) and HCQ (200 mg po twice daily) as maintenance therapy for half a year. The patient's condition was improved after prednisone treatment. However, the symptoms recurred when the prednisone treatment was stopped. The details of the laboratory investigations and ongoing treatments are shown in  Figure 1 .
Six months previously, skin ulcers developed on the two lower limbs, progressively worsening, and the effect of glucocorticoid treatment was not effective as prior treatments. When the dose of prednisone was reduced by 25 mg daily or lower, the skin ulcers exacerbated. The condition of the skin ulcers is shown in  Figure 2A . Physical examination in our hospital revealed a symmetrical rash in the calf area, accompanied by visible erythema (size, 2-5 mm). The skin lesions were not tender and swollen. There was no joint pain, Raynaud's phenomenon, and mucosal involvement. In addition, there were no apparent abnormalities on general examination. Laboratory investigations were as follows: white blood cells: 4.50 x 109/L (neutrophil: 2.54 x 109/L, lymphocyte: 1.48 x 109/L, and eosinophil: 0.19x109/L), hemoglobin: 118 g/L, platelet count: 291 x 109/L, erythrocyte sedimentation rate (ESR): 12 mm/h, C-reactive protein (CRP): 16.3 mg/L, antistreptolysin O test: 160 IU/mL, rheumatoid factor: < 20.0 IU/mL, circulating immune complexes: 2.55 RU/Ml. Anti-myeloperoxidase antibodies, anti-proteinase 3 antibodies, anti-glomerular basement membrane antibodies, anti-dsDNA antibodies, ANCA were all negative. Human immunodeficiency virus, syphilis, hepatitis B, and hepatitis C were also negative. Complement level, urinalysis, and carcinoembryonic antigen test were within normal values.
Given the effectiveness of JAK inhibitor tofacitinib in patients with RA and psoriasis, the patient started a treatment regimen that comprised tofacitinib (5 mg po twice daily) and prednisone (25 mg po daily). One month later, the symptoms improved steadily on this regimen ( Figure 2B ). Complete remission of skin ulcers was achieved after 2 months ( Figure 2C ). The patient stopped taking glucocorticoid treatment, and no evidence of recurrence or side effects was observed throughout the 6 months of follow-up ( Figure 2D ). The follow-up laboratory results indicated significant improvement in inflammatory biomarkers (ESR: 6 mm/h, CRP: 4.5 mg/L). Accordingly, our findings supported the efficacy of tofacitinib in this case investigation.