A retrospective review of electronic medical records of patients diagnosed with IIM seen at The University of Kansas Medical Center between January 2005 to March 2018. IIM patients were identified via HERON, the research informatics platform for our electronic medical records at KUMC.

Two hundred and ninety-four patients were identified in total. Patient who did not have evidence of IIM were excluded. The new cohort, 94 patients, was predominantly females (72F vs 22M) with a mean age of 55.5 ± 15.3. The most common IIM subtype was dermatomyositis (DM) (44.6%) followed by non-specific myositis (NSM) (23%), necrotizing myopathy (NM) (22.3%), and polymyositis (PM) (9.5%). Ten out of ninety-four patients (10.6%) had antisynthetase syndrome (ASS) commonly associated with NSM (60%). Anti-Jo1 was the most common muscle specific antibody (MSA) found in ASS (50%) but its presence was not specific to ASS. Anti-PL7 (40%) and anti-PL12 (10%) were specifically found in ASS.  Eighteen out of ninety-four (19%) patients had interstitial lung disease and it was associated mainly with anti-SSA  (NSM=4/PM=2/DM=2) and anti-Jo1 antibodies (NSM=3/DM=1). Overall, four MSAs were associated with specific IIM subtypes, anti-HMGCR and anti-SRP in NM, and anti-PL12 and anti-NXP2 in DM. The remaining MSAs were not limited to one IIM subtype. All positive anti-KU (NSM=2) and anti-MDA5 (NM=1/NSM=1) patients had cancer. Irritative myopathy on EMG was found in 94.6% of all IIM patients.

In our cohort, few MSAs were specific to one type of IIM but most MSAs were not. Two MSAs, anti-KU and anti-MDA5, were strongly associated with cancer.