A 42-year-old man comes to the emergency department due to 4 days of nausea, skin rash, progressive weakness, and decreased urine output. For the past few months he has also had fatigue, tingling in his hands and feet, and occasional joint pains. The patient has had no fever, chest pain, dysuria, hematuria, or diarrhea. He has no chronic medical problems and takes no medication. The patient does not use tobacco or alcohol but used injection drugs during his early 20s. Temperature is 37.6 C (99.8 F) , blood pressure is 150/90 mm Hg, pulse is 92/min, and respirations are 16/min. BMI is 24.8 kg/m². Mucous membranes are dry with no lesions. Cardiopulmonary auscultation is normal. The liver edge is palpable 2 cm below the right costal margin. Bilateral ankle reflexes are absent. He has mild, bilateral, lower-extremity pitting edema and a palpable, nonblanchable, purpuric rash on both legs. There is no joint swelling or erythema. Laboratory results are as follows:

Which of the following is most helpful in establishing the cause of this patient's renal dysfunction?

Question

A 42-year-old man comes to the emergency department due to 4 days of nausea, skin rash, progressive weakness, and decreased urine output. For the past few months he has also had fatigue, tingling in his hands and feet, and occasional joint pains. The patient has had no fever, chest pain, dysuria, hematuria, or diarrhea. He has no chronic medical problems and takes no medication. The patient does not use tobacco or alcohol but used injection drugs during his early 20s. Temperature is 37.6 C (99.8 F) , blood pressure is 150/90 mm Hg, pulse is 92/min, and respirations are 16/min. BMI is 24.8 kg/m². Mucous membranes are dry with no lesions. Cardiopulmonary auscultation is normal. The liver edge is palpable 2 cm below the right costal margin. Bilateral ankle reflexes are absent. He has mild, bilateral, lower-extremity pitting edema and a palpable, nonblanchable, purpuric rash on both legs. There is no joint swelling or erythema. Laboratory results are as follows:

Which of the following is most helpful in establishing the cause of this patient's renal dysfunction?

Quizplus · Accepted Answer

Explanation: This patient has renal insufficiency with palpable purpura, elevated rheumatoid factor, and hypocomplementemia, raising suspicion for mixed cryoglobulinemia syndrome. The diagnosis can be confirmed by measuring serum cryoglobulin levels. Mixed cryoglobulinemia syndrome is a vasculitis due to the deposition of immune complexes (polyclonal IgG and IgM rheumatoid factor) within the vascular wall of small- and medium-size vessels. Most cases arise in those with chronic hepatitis C virus (as is likely in this patient with a history of intravenous drug use), but patients with lymphoproliferative disorders, autoimmune disease, and other infections are also at risk. Patients with mixed cryoglobulinemia syndrome most commonly develop a triad of manifestations: Palpable purpura Weakness Arthralgias Other nonspecific symptoms (eg, nausea) and peripheral neuropathy also frequently occur. Laboratory examination typically reveals elevated rheumatoid factor and hypocomplementemia. Approximately 20% of patients develop glomerulonephritis (red cells, red cell casts, proteinuria) with or without renal insufficiency. (Choice A) Testing for antineutrophil cytoplasmic antibodies can help diagnose granulomatosis with polyangiitis and microscopic polyangiitis. These small-vessel vasculitides typically cause palpable purpura, glomerulonephritis, renal insufficiency, and fatigue. However, they are usually associated with normal or elevated (not low) complement levels and respiratory tract symptoms (eg, sinusitis, rhinorrhea). (Choice B) Elevated anti-dsDNA antibodies are often seen in patients with systemic lupus erythematosus (SLE). SLE can cause fatigue, arthralgias, renal insufficiency, glomerulonephritis, and low complements levels, but palpable purpura is uncommon. Patients with SLE are more likely to have malar rash or discoid lesions. malar rash discoid lesions (Choice C) Antiglomerular basement membrane antibodies are seen in Goodpasture disease, which is associated with acute glomerulonephritis. Patients typically have pulmonary symptoms (eg, alveolar hemorrhage, hemoptysis), and systemic symptoms are rarely present. (Choice E) A streptozyme test can evaluate for a streptococcal infection, which can cause poststreptococcal glomerulonephritis due to immune complex deposition. Manifestations include renal insufficiency, nephritis, and low C3 complement levels. However, most patients have normal C4 complement levels and a recent history of streptococcal pharyngitis or skin infection. In addition, palpable purpura is uncommon. Educational objective: Mixed cryoglobulinemia syndrome is typically associated with chronic hepatitis C virus infection and usually manifests with the triad of palpable purpura, fatigue, and arthralgias. Peripheral neuropathy, systemic symptoms, and glomerulonephritis with renal insufficiency are also common. Diagnosis is typically made by measuring serum cryoglobulin levels. References: Therapy for hepatitis C virus-related cryoglobulinemic vasculitis. (http://www.ncbi.nlm.nih.gov/pubmed/24024840)

A 42-Year-Old Man Comes to the Emergency Department Due to 4