Antinuclear antibodies are autoantibodies directed against cellular autoantigens. They are detected by indirect immunofluorescence technique. In case of positivity, the antigenic target must be identified. In this work we report the case of antinuclear antibody positivity without defined antigenic target. The patient was 56 years old and came to the department of internal medicine because of a worsening of her late-onset asthma, which had been followed for 3 years, with the appearance of myalgias, arthralgias, photosensitivity and dry eyes, which led to the suspicion of an autoimmune disease. Biological examinations showed an elevation of CRP and sedimentation rate, normal blood count, normal hemostasis, renal and hepatic tests were also without particularities. Immunological tests for rheumatoid factor and anti-CCP antibodies were negative. The anti-nuclear antibody test was positive on two occasions at 640 and 1280 with a homogeneous appearance. However, the complementary workup to identify antinuclear antibodies was negative: anti-native Dna antibodies, anti-soluble antigen antibodies and myositis profile. Finally, the search for anti-neutrophil cytoplasmic antibodies was positive for p- ANCA with a value greater than 1280. The diagnosis of Churg-Strauss type ANCA vasculitis was retained in our patient in view of the clinical symptoms presented and the positive immunological assessment for p-ANCA.