The results of routine laboratory studies, including urinalysis, complete blood cell counts, liver function tests, and serum electrolyte, serum urea nitrogen, fasting serum glucose, and C-reactive protein levels, were normal. Serologic test results for syphilis were negative. Her serum IgG level increased to 2780 mg/dL (normal, 850-1770 mg/dL), but her IgA and IgM levels were normal. The titers of antinuclear antibody decreased to 160 arbitrary units per milliliter, and the titer of anti–double-stranded DNA antibody also decreased to 36 arbitrary units per milliliter. Antibodies against U1RNP, Sm antigens, SS-A/Ro, SS-B/La, myeloperoxidase antineutrophil cytoplasmic antibody, proteinase 3 antineutrophil cytoplasmic antibody, single-stranded DNA, and cardiolipin were negative. Levels of complements were as follows: C1q, undetectable level; C1r, 20.1% (normal level, 40%-140%); C1s, 21.4% (normal level, 45%-130%); C2, undetectable level; C3, 70 mg/dL (normal level, 80-160 mg/dL); C4, 1 mg/dL (normal level, 15-40 mg/dL); and total CH50 hemolytic activity, 2 U/mL (normal level, 30-55 U/mL). The plasma level of C1INH was less than 2 mg/dL (normal, 10-25 mg/dL), and the C1INH activity was less than 25% (normal level, 80%-125%). The cerebrospinal fluid showed a lymphocyte count of 3.0 × 10−3/μL, a total protein level of 1.18 × 10−1 g/dL (normal level, <4.0 × 10−2 g/dL), an IgG level of 32.9 mg/dL (normal level, 1-4 mg/dL), and an IgG index of 0.75 (normal index, <0.70). The results of nerve conduction studies on 6 peripheral nerves confirmed a diagnosis of sensorimotor axonal mononeuritis multiplex. Ischemic lesions or contrast enhancement were not found on magnetic resonance images of the brain and spinal cord.