La ricerca degli anticorpi anti-nucleo non è sempre di facile interpretazione

Antinuclear antibodies (ANA) displaying dense fine speckled pattern on HEp-2/HEp-2000 cells are frequently observed in clinical laboratory, often associated with anti-DFS70 antibodies. Anti-DFS70 positive patients rarely develop systemic autoimmune rheumatic disease, especially in the absence of clinical evidence or additional antibodies. A 60-years old woman complaining severe muscle weakness of the legs was tested positive for dense fine speckled ANA pattern by indirect immune-fluorescence. Immunoblot analysis revealed the presence of anti-DFS70 antibodies. Positivity for anti-dsDNA antibodies, not revealed by immunoblot, was also found by Crithidia luciliae (CL). All the results were confirmed by a different laboratory. This case underlines the complex interpretation of a laboratory scenario where anti-DFS70 possibly coexist with much more specific and clinically relevant ANA. The discrepancies (observed in both laboratories) between CL and the other methods is puzzling, and may be due to different reasons, including false positive CL results or interference.