Abstract
Anti-HMGCR-positive immune-mediated necrotizing myopathy (IMNM) was initially considered as an exclusively skeletal muscular disease characterized by predominant proximal muscle weakness, observed in elderly patients with an acute duration. However, an increasing number of patients presented extra-muscular involvements coinciding with other autoimmune antibodies. Moreover, some juvenile patients showed chronic weakness of shoulder and hip girdle musculature, resembling limb-girdle muscular dystrophy (LGMD). The present study aims to develop the essential and easily available clinical-pathological classification for anti-HMGCR-positive IMNM patients. Eighteen anti-HMGCR-positive IMNM patients were from Nanfang Hospital and fifty were from published studies. We separated patients into two subgroups, including the overlap (with coexistence of other antibodies) and non-overlap groups (with only anti-HMGCR-positive patients). Medical information, including the clinical and pathological features, together with their treatments and prognosis were compared. We found that compared to the non-overlap anti-HMGCR-positive IMNM group, overlap patients had more extra-muscular symptoms, corresponding to the coexistence of other myositis-specific antibodies (MSAs) and resulting different treatments and prognoses. The early onset age and chronic process, together with the special pathology of resembling LGMD indicated that this is likely a different subtype in non-overlap anti-HMGCR-positive IMNM patients. The results revealed that the anti-HMGCR-positive IMNM patients can be separated into overlap and non-overlap anti-HMGCR-positive IMNM patients. The non-overlap group can be further divided into LGMD-like and non-LGMD-like anti-HMGCR-positive IMNM. However, the confirmed classification of anti-HMGCR-positive IMNM patients requires further proteomics and transcriptomics studies and could potentially be useful for individualized treatment decision making.