Differential Diagnosis

The patient's presentation of >50 WBC, hematuria, and proteinuria, along with the presence of anti-dsDNA antibodies and a negative culture, suggests an autoimmune or inflammatory process. Here's a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Lupus Nephritis: The presence of anti-dsDNA antibodies is highly suggestive of Systemic Lupus Erythematosus (SLE), and the combination of hematuria, proteinuria, and elevated WBC count points towards renal involvement, making lupus nephritis the most likely diagnosis.

• Other Likely Diagnoses

  • Vasculitis (e.g., ANCA-associated vasculitis): Although the presence of anti-dsDNA antibodies leans more towards SLE, vasculitis could also present with similar renal findings and elevated WBC count. The absence of a positive culture reduces the likelihood of an infectious cause but does not rule out vasculitis.
  • Post-infectious Glomerulonephritis: Despite the negative culture, it's possible that the infection was cleared, or the culture was a false negative. This condition could still be considered, especially if there's a recent history of infection.

• Do Not Miss Diagnoses

  • Sepsis: Although the culture is negative, sepsis can present with elevated WBC counts, and renal involvement could lead to hematuria and proteinuria. It's crucial to rule out sepsis due to its high mortality rate if untreated.
  • Endocarditis: Similar to sepsis, endocarditis can have a varied presentation, including renal manifestations due to embolic phenomena or immune complex deposition. A negative blood culture does not rule out endocarditis, especially if the patient has a history of valvular heart disease.

• Rare Diagnoses

  • Goodpasture Syndrome: An autoimmune disease characterized by the presence of anti-GBM antibodies, which could present with renal and pulmonary manifestations. It's less likely given the presence of anti-dsDNA antibodies but should be considered in the differential.
  • IgA Nephropathy (Berger's disease): Could present with hematuria and proteinuria, but the presence of anti-dsDNA antibodies and the clinical context make this less likely. However, it remains a possibility, especially if there's a family history or recurrent episodes of hematuria.