Clinical and imaging differences between limb⁃girdle muscular dystrophy type 2B and immune⁃mediated necrotizing myopathy

Abstract

Objective To investigate the clinical and imaging differences between limb⁃girdle muscular dystrophy type 2B (LGMD2B) and immune⁃mediated necrotizing myopathy (IMNM). Methods Forty⁃five patients with LGMD2B and 45 patients with IMNM from January 2014 to December 2018 were included. Sex, age of onset, age of diagnosis and time of delay in admission were recorded, and serum creatine kinase (CK) level was measured. Cervical flexion, proximal and distal upper limbs, proximal and distal lower limbs were evaluated by Medical Research Council (MRC) Level 6 and muscle strength percentages were calculated. Skeletal muscle fatty infiltration and edema degree on both thighs were evaluated by MRI. Results The onset age (Z=⁃3.605, P=0.000) and diagnosis age (Z=⁃2.757, P= 0.006) of LGMD2B patients were earlier than those of IMNM patients, while the delay time of admission was longer than that of IMNM patients (Z=⁃4.749, P=0.000), the serum CK was higher than that of IMNM patients (Z=⁃2.247, P=0.025). The muscle strength of neck flexion (Z=⁃6.320, P=0.000)and percentage of muscle strength(t=⁃6.320, P=0.000),the muscle strengh of proximal uppe rextremities (Z=⁃3.528, P= 0.000)and percentage of muscle strength (t=⁃3.762, P=0.000)in IMNM patients were lower than those in LGMD2B patients, while the muscle strengh of distal lower extremity (Z=⁃ 3.256, P=0.001) and percentage of muscle strength (t=⁃2.883, P=0.004) in LGMD2B patients were lower than those in IMNM patients. LGMD2B patients had higher muscle fatty infiltration degree in anterior group (Z=⁃3.119, P= 0.002)and posterior group (Z=⁃2.534, P=0.011)of thigh muscle than IMNM patients, but IMNM patients had highter thigh muscle edema degree in posterior group than LGMD2B patients (Z=⁃3.887, P=0.000). Conclusions Compared with IMNM patients, LGMD2B patients had earlier onset age, longer delay in diagnosis time, worse muscle strength of distal lower extremities, higher serum CK and more obviously thigh muscle fatty infiltration. In IMNM patients, muscle weakness of neck flexion and proximal upper extremities, thigh muscle edema of posterior group were more obvious. These characteristics contribute to the clinical differentiation of the two diseases.

DOI：10.3969/j.issn.1672⁃6731.2020.09.004