Cancer screening in idiopathic inflammatory myopathies: Ten years experience from a single center.

OBJECTIVE: There is a well-recognized association between cancer and myositis, so cancer screening at diagnosis is recommended. We aim to report the results of our cancer screening strategy and to ascertain the reliability of using PET/CT to identify cancer-associated myositis (CAM) in a large cohort of patients with myositis from a single center over 10 years. METHODS: This retrospective observational study included all patients diagnosed with any type of myositis except for inclusion body myositis. Cancer screening strategy was individualized according to clinical and serological data, including PET/CT as the main test to detect occult cancer (OC). Procedures derived from a positive PET/CT were registered. Qualitative data expressed as percentages, and quantitative data as the median with the interquartile range were analyzed. A ROC curve was used to estimate the reliability of PET/CT for CAM diagnosis. RESULTS: Seventy-seven out of 131 patients underwent a PET/CT for OC screening. The performance of the PET/CT in patients with myositis at disease onset yielded an area under the curve ROC of 0.87 (0.73-0.97) for CAM diagnosis. Invasive procedures in 7 (9%) patients without a final diagnosis of cancer did not cause derived complications. Patients not evaluated for OC did not develop cancer after a median follow-up of 3.3 years (1.7-6.7). CONCLUSION: Cancer screening strategy should be individualized. PET/CT at myositis onset seems to be an efficient approach to rule out CAM. This practice does not seem to significantly increase harm to patients related to the additional tests needed to clarify inconclusive results.

Statin-associated autoimmune myopathy: A distinct new IFL pattern can increase the rate of HMGCR antibody detection by clinical laboratories.

BACKGROUND AND OBJECTIVE: Statin-associated autoimmune myopathy (SAAM) with anti-HMGCR antibodies has recently been described. Several specific immunoassays are in use to detect HMGCR antibodies. In the course of systematic autoantibody screening we recognized a new distinct IFL staining pattern on rat liver sections that regularly coincided with anti-HMGCR antibodies. In this study we investigated whether this new IFL pattern is specifically associated to statin-associated autoimmune myopathy and corresponds to anti-HMGCR antibodies. PATIENTS AND METHODS: Twenty-three patients positive for anti-HMGCR antibodies (14 diagnosed with SAAM) were investigated for anti-HMGCR antibodies by two ELISA assays and confirmed by immmunoblot. HMGCR associated liver IFL pattern (HALIP) was detected by indirect IFL and the reactivity against HMGCR was confirmed by immunoabsorption using purified human HMGCR antigen. 90 patients with other autoimmune diseases and 45 non-autoimmune statin treated patients were studied as controls. RESULTS: 21 out of 23 (91%) anti-HMGCR positive patients were HALIP positive. The staining was completely and specifically removed by immunoabsorption with human purified HMGCR. None of the control sera from autoimmune patients or non-autoimmune statin treated subjects was positive for HALIP. Statistical concordance between HALIP and anti-HMGCR antibody specific tests was 98.7%, kappa 0.95. CONCLUSIONS: A new and distinct IFL staining pattern (HALIP) is associated to HMGCR associated myopathy. Absorption and concordance studies indicate that the antigen recognized in the liver by HALIP is HMGCR or a closely related protein. Awareness of this new pattern can help to detect HMGCR autoantibodies in statin treated patients tested for autoimmune serology.