Table 1

General features of the patients included in the study

IMNMIBM (n=153)PM (n=176)DM (n=219)CADM (n=17)Total (n=666)
Total (n=101)HMGCR (n=50)SRP (n=22)
Age at onset48.9 (16.0)53.3 (13.1)***38.4 (13.1)***58.4 (10.8)***50.8 (15.9)45.4 (14.2)***48.7 (14.9)50.4 (15.0)*
Length of illness (years)4.3 (5.8)4.3 (5.8)3.5 (4.0)7.8 (6.7)***5.6 (7.2)3.8 (4.7)***2.2 (3.0)*5.2 (6.3)*
Female sex65% (66)64% (32)86% (19)38% (58)***66% (116)76% (167)***82% (14)63% (421)
White69% (70)*78% (39)59% (13)88% (134)***69% (122)**81% (177)71% (12)77% (515)
Black19% (19)*14% (7)36% (8)7% (10)*20% (35)***8% (17)*6% (1)12% (82)
Other races12% (12)8% (4)5% (1)6% (9)*11% (19)11% (25)24% (4)10% (69)
  • Continuous variables are expressed as mean (SD) and bivariate variables as percentage (absolute number). The value of each major clinical group (IMNM, IBM, PM, DM and CADM) was compared with the rest of the sample. In separate analyses, patients with anti-HMGCR and anti-SRP were compared with each other only. The χ2 test and Fisher’s exact test were used to compare bivariate variables. Continuous variables were compared using Student’s t-test. The length of illness was measured from the onset of first symptoms to the date of the thigh MRI.

  • *<0.05; **<0.01; ***<0.001.

  • CADM, clinically amyopathic dermatomyositis; DM, dermatomyositis; HMGCR, HMG-CoA reductase; IBM, inclusion body myositis; IMNM, immune-mediated necrotising myopathy; PM, polymyositis; SRP, signal recognition particle.