Antinuclear antibody-negative systemic lupus erythematosus: loss in body fluids.

Repeated determination for antinuclear antibody (ANA) were negative in a patient with systemic lupus erythematosus (SLE) and severe multisystem involvement including diffuse proliferative glomerulonephritis and the nephrotic syndrome. However, concentration of urinary protein, of pleural fluid and subsequently of serum revealed ANA. This case demonstrates another cause of a false negative ANA in SLE--a low concentration of the antibody in serum and loss in body fluids.