A 50-year-old man is evaluated in the hospital for fatigue, joint pain, and skin lesions. His symptoms started 2 weeks ago with fever and sore throat, which subsided in 2 days. Fatigue and joint pain were noted 1 day after the onset of sore throat, which worsened over the subsequent days. Four days after the onset of symptoms, he noted dark red spots on his ankles and shins, which spread to involve his legs, thighs, and buttocks; the skin lesions were not painful or itchy. He also notes intermittent central abdominal pain, crampy in nature and not related to food. He has hypertension that was previously well controlled with lisinopril and hydrochlorothiazide.
On physical examination, temperature is 37.8 °C (100.0 °F), blood pressure is 170/84 mm Hg, pulse rate is 78/min, and respiration rate is 14/min. BMI is 28. Examination of the joints shows tenderness and increased warmth in the knees, ankles, and elbows without effusions. Cardiac and lung examinations are normal. There is mild guarding around the periumbilical area on abdominal examination.
The appearance of the skin is shown.
Albumin | 3.1 g/dL (31 g/L) |
Complements (C3 and C4) | Normal |
Creatinine | 1.8 mg/dL (159 µmol/L) |
Hepatitis B antibody profile | Negative |
Hepatitis C antibody profile | Negative |
Urinalysis | 3+ blood; 2+ protein; 50-100 erythrocytes/hpf; 10-15 leukocytes/hpf; few erythrocyte casts |
Urine protein-creatinine ratio | 2200 mg/g |
Lupus serologies, antistreptolysin O antibodies, ANCA, and anti–glomerular basement membrane antibodies are pending. Blood cultures are pending. Stool occult blood test is positive.
Which of the following is the most likely diagnosis?