ANCA seropositivity in HIV: a serological pitfall.

In systemic vasculitis, cytoplasmic staining in ethanol-fixed neutrophilic granulocytes, i.e. cytoplasmic antineutrophilic cytoplasmic antibody (c-ANCA), is generally considered a highly significant serological marker. When a patient presents with upper airway or renal symptomatology and seropositivity to c-ANCA, a Wegener's granulomatosis is usually easily diagnosed by performing a biopsy of the diseased organ. However, not every ANCA-positive patient with pulmonary inflammation is suffering from Wegener's disease. In some cases of upper airway or pulmonary symptomatology, the a priori chance of having Wegener's disease is low despite a positive ANCA. A coincidental positivity of ANCA may then lead to clinicians jumping to conclusions. We present a 40-year-old man who was falsely suspected of having Wegener's disease because of upper airway symptomatology and c-ANCA positivity. Specificity analysis revealed that he was negative to antibodies for proteinase-3, but positive to myeloperoxidase. The potential serological pitfall of the supposedly specific c-ANCA is discussed.